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UNIVLR5ITY  OF  ILLINOIS  BULLLTIN 


Vol.  X.  SEPTEMBER  9,  1912.  No.  2 


[Lntered  February   14,  1902,  at  Urbana,  Illinois,  as  second-class  matter  under 
Act  of  Congress  of  July  16,  1894.] 


BULLLTIN  No.  16 
DLPARTMLNT  OF  CERAMICS 

A.  V.  BLE.ININGLR,   Director 


COBALT  COLOR5  OTHLR  THAN  BLUL 

BY 
R.  T.  STULL  AND  G.  H.  BALDWIN 


INFLULNCL5  OF  VARIABLE  5ILICA  AND  ALUMINA 

ON    PORCELAIN   GLAZE5   OF 

CONSTANT  RO 


BY 
R.  T.  STULL 


INVESTIGATIONS  ON    THE  DIELECTRIC 
STRENGTH  OF  SOME  PORCELAINS 


BY 
B.  S.    RADCLIFFL 


1911-1912 


PUBLISHED  FORTNIGHT .Y  BY  THE  UNIVERSITY       >A 


7io.lL-23 

[Reprinted  from  Transactions  American  Ceramic  Society,     Vol.  XIV, 
by  Permission.] 

COBALT  COLORS  OTHER  THAN  BLUE. 

By  R.  T.  Stull  and  G.  H.  Baldwin,  Ceramic  Laboratories, 

University  of  Illinois. 

INTRODUCTION. 

The  color  imparted  to  a  glass  or  glaze  depends  upon  the  kind 
of  coloring  oxide,  the  composition  of  the  batch  and  the  manner 
of  heat  treatment.  It  has  been  considered  that  cobalt  is  per- 
sistent in  producing  blue  under  all  conditions.  Since  two  or 
more  distinct  colors  are  obtainable  from  all  other  coloring  oxides 
under  different  conditions,  there  seemed  to  be  no  logical  reason 
why  some  color  other  than  blue  could  not  be  obtained  from 
cobalt  oxide. 

Since  cobalt  oxide  has  so  persistently  given  blue  colors  under 
normal  ceramic  practice,  it  was  evident  that  a  departure  in  com- 
position must  be  made  from  the  ordinary  commercial  types  of 
glazes  if  a  color  different  from  blue  was  to  be  developed  from 
cobalt  oxide. 

A  speculation  as  to  the  possible  colors  obtainable  from  cobalt 
oxide  as  the  sole  colorant  is  of  interest.  Cobalt  salts  in  solution 
under  certain  conditions  impart  pink,  while  under  other  conditions 
the  color  imparted  is  blue.  It,  therefore,  seemed  possible  to  de- 
velop all  the  different  shades  from  blue  on  one  hand  to  pink  or 
even  light  red  on  the  other.  The  problem  was  to  develop  a  type 
of  glaze  that  would  bring  out  the  pink  or  red  color  if  such  were 
possible,  and  the  key  to  the  situation  was  found  in  blowpipe 
analysis.  Magnesia  and  magnesium  minerals  containing  cobalt, 
when  powdered,  moistened  with  a  solution  of  cobalt  nitrate  and 
heated,  give  a  pink  color.  Alumina  and  alumina  minerals 
containing  cobalt,  when  similarly  treated,  give  blue. 

This  suggested  a  glaze  high  in  magnesia  and  free  from  alumina. 
It  was  recognized  that  if  such  colors  could  be  produced  they  would 
be  of  greatest  value  for  low  temperature  work.  Since  a  high 
content  of  magnesia  imparts  refractoriness  to  a  glaze,  it  would 
be  necessary  to  introduce  a  "softener"  which  would  not  in- 
fluence the  color  toward  the  blue.  Of  the  two  "softeners," 
PbO  and  B,03,  tried  in  a  preliminary  test,1  it  was  found  that  the 


1  Vol.  XII.  Trans.  A.  C  S.,  pp.  707-708. 


COBALT  COLORS  OTHER  THAN  BLUE. 


former  changed  the  magnesia-cobalt  pink  to  blue,  while  the  latter 
did  not,  hence  B203  was  selected  as  the  "fluxing"  or  "softening" 
agent. 

EXPERIMENTAL  WORK. 
First  Group. — The  first  group  of  glazes  was  made  in  order 
to   develop   workable   members   over   a   range   of   temperatures. 
In  this  group   the   RO   remained   constant,   the  Si02  and   B203 
being  variables.     The  limits  covered  were 


o .  2  Na20 
o .  6  MgO 
o .  2  CoO 


o  to  i.o  B20„    i  .o  to  4.0  Si02. 


Twenty-four  glazes  were  made  in  this  group.  The  horizontal 
series  are  designated  by  letters  and  the  vertical  series  by  numbers 
(see  charts).  The  formula  and  batch  weights  of  the  four  corner 
glazes  are: 

Formulae  Batch  weights 


0 

q 

O 

c 

O 

c 

0 
0 

O 

u 

M 

c 

"5 

C 

4-» 

z 

§ 

0 

pa 

CO 

Z 

£ 

u 

m 

h 

A-i 

0.2 

O.6 

0.2 

0 

1 .0 

2  12 

504 

165 

600 

A-6 

0.2 

O.6 

0.2 

1 .0 

1 .0 

212 

504 

165 

1240 

600 

D-i 

O.  2 

O.6 

O.  2 

0 

4.0 

212 

504 

165 

2400 

D-6 

O.  2 

O.6 

O.  2 

1 .0 

4.0 

212 

504 

165 

1240 

2400 

The  four  batches  were  weighed,  ground  dry  for  one  hour, 
fritted  and  ground  to  pass  120  mesh.  The  different  members 
in  the  group  were  made  by  blending  the  four  extremes  according 
to  their  combining  weights. 

Since  the  glazes  settled  rapidly  and  caked,  it  was  found 
necessary  to  employ  a  "colloid"  in  order  to  induce  flotation  for 
application  and  adhesion  on  drying.  Glucose,  dextrine  and  glue 
were  tested.  The  best  results  were  obtained  with  4-5  per  cent, 
glue.  Such  large  quantities  of  either  glucose  or  dextrine  were 
required  in  order  to  produce  free  flotation  that  the  glazes  cracked 
and  curled  up  on  drying.  With  glue,  however,  a  high  degree  of 
flotation  was  obtained,  and  the  glazes  dried  without  cracking. 

The  glazes  were  applied  in  a  thick  coat  on  2"  porcelain  discs 
previously  burned  to  cone  1 1 .  Three  burns  of  this  group  were 
made,  viz.,  cones  2,  4  and  7    (Charts  1,  2  and  3).      At   cone    2 


COBALT  COLORS  OTHER  THAN  BLUE. 


T/^A/s. s4/w.  C£~s? sac  ro/L .  ^/^  srt/£ s.  <*•  0^/.a^/M 


mm 


A/ 

A2 

A3 

A<4- 

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Q 

\ 

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<& 

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A7<?£J£<Z<y/-j£'^  <^?  Of 


COBALT  COLORS  OTHER  THAN  BLUE. 


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COBALT    COLORS    OTHER    THAN    BLUE. 


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8  COBALT  COLORS  OTHER  THAN  BLUE- 

(Chart  i)  members  C  6,  B  5,  B  6,  A  5  and  A  6  were  well  matured. 
A  4  and  B  4  were  well  vitrified,  presenting  pleasing  matte  surfaces. 
Refractoriness  increases  on  a  line  from  A  6  to  D  1 .  Member  A  6 
is  a  deep  "red-violet"  in  color,  showing  more  of  the  red  than  the 
blue.  When  we  pass  in  any  direction  from  A  6  upward  or  to  the 
left,  the  red  diminishes  and  the  blue  increases. 

At  cone  4  (Chart  2)  the  field  of  matured  glazes  has  not 
materially  broadened.  A  4  and  B  4  are  still  matte  but  their 
surfaces  have  changed  from  an  "egg  shell"  texture  to  a  promis- 
cuously interlacing  needle  crystal,  surface. 

At  cone  7  (Chart  3)  the  matured  field  has  broadened  only  a 
little.  A  5  and  A  6  have  reached  a  high  state  of  fluidity,  have 
flown  down  over  the  sides  of  the  trials  and  are  deep  blue  in  color 
with  a  few  spots  of  the  red-violet  here  and  there.  These  glazes 
show  that  they  have  attacked  the  body  vigorously.  In  all  three 
burns  crystallization  is  quite  prominent  and  brings  out  the  red- 
violet  color. 

The  results  of  this  group  indicate  that  a  decrease  in  SiO, 
and  an  increase  in  B203  tends  toward  diminishing  blue  and  in- 
creasing red,  and  that  2  molecules  of  Si02  as  a  maximum  and 
0.6  molecule  of  B,03  as  a  minimum  are  the  approximate  limits 
in  these  directions  for  glazes  that  will  mature  well  at  or  below 
cone  7. 

Second  Group. — A  second  group  was  constructed  with  the 
idea  of  bringing  out  more  of  the  red  and  less  of  the  blue  and  to 
develop  glazes  maturing  at  lower  temperatures.  This  group, 
in  which  the  constant  RO  is  the  same  as  in  the  first  group,  covered 
the  following  limits : 

o .  2  Na20 

o .  6  MgO     [  o .  6  to  1.4  B,03,  o .  5  to  1.5  Si02 

o .  2  CoO     J 

Twenty-five  members  were  made,  A  6  of  the  first  group  being 
stationed  at  the  center  and  having  the  new  nomenclature  of  G3. 
The  members  were  blended  from  the  four  previously  fritted 
extremes,  the  same  as  was  done  in  the  first  group.  The  formulae 
and  batch  weights  of  the  four  extremes  are : 


COBALT  COLORS  OTHL'R  THAN  BLUE. 


T/?^/V5.  s4A>f.  C^/?.  >SC?C.  y<P/L  .  sT/ls  STZ//L/L  <S.  &4<U?H///V 


// 


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/3  /^  S^5 


(J  ///  //<?  /<^  /y^z  ms 


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/=■*?       /=^ 


/=~^ 


&/         £^        ^J        £* 

*  <fc  ^>  Jl 

<s         3         x  x 


io 


COBALT  COLORS  OTHER  THAX  BLUE. 


r/=?A/VS.s4A*.  C£T/?.  SOC  A2PZ. .  */ls  S7~£SZ_L_  <S.  &s4/.£>tV/A/ 

.  GAst&O  \  CO/VST^ A/7~ 
^^^       2COOJ 


/-5» 


1/  re  13  i^- 


i^ 


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SZ              jE3              ^<4- 

<0 

<b                 ^                  M 

Q 

S                         V                         N 

Af0KJEC£AL£S  &<?&3 

COBALT  COLORS  OTHER  THAN  BLUE. 


II 


TRA  A/S.  AM.  C£T/?.  SOC.  YOL  X/f  SrVL  L  &  &AL  DW//V 

^_  _  CO/V&  3  &C/RA/ 

6M&0  \COA/STAA/r 
■  2CoO  J 


/.50 

// 


/.25 


-z'L 


/2  /3  /^  fS 


HI 

^      G/ 


9^9 


H2  /-?3  H4-  MS 


G2  03  G<4-  OS 


S3  B3  /^4-  BS 

mmmmm 

S/  S2  S3  S<4-  SS 

<0  <6  ^  (\j  > 

S  S  x  ^  ^ 


12 


COBALT  COLORS  OTHER  THAX  BLUE. 


Formulae 

Batch  weights 

O 

0 
§ 

o 

so 

5= 

0 

0 

<-> 

pq 

o 
35 

0 

0 
a 

M 

S 

0 

0 
0 

s 

to 

q 

E-i 

0.2 

o.6 

0.2 

o.6 

o-5 

212 

504 

165 

744 

300 

E-5 

O.  2 

o.6 

O.  2 

i-4 

°-5 

2  12 

504 

165 

i860 

300 

I-i 

O.  2 

o.6 

O.  2 

o.6 

i-5 

212 

504 

165 

744 

900 

1-5 

0.2 

o.6 

O.  2 

1.4 

i-5 

212 

504 

165 

i860 

900 

Three  burns  were  made,  viz.,  cones  02,  1  and  3  (Charts 
4,  5  and  6).  The  red-violet  color  was  well  developed  in  all  cases 
except  in  vertical  series  1,  containing  0.6  B203,  which  remained 
persistently  matte  in  all  three  burns.  Crystalline  patches  appear 
in  all  pieces  where  well  matured.  The  red- violet  color  is  more 
prominent  where  crystallization  has  taken  place.  Decreasing 
Si02  and  increasing  B203  tends  to  throw  the  color  toward  the 
red  and  away  from  the  blue  the  same  as  observed  in  the  first 
group.  Where  the  glazes  are  overtired,  they  have  "run"  con- 
siderably, attacked  the  body  and  give  a  clear  blue.  Occasionally 
a  small  group  of  red- violet  crystals  appear  in  a  clear  blue  field. 

Several  of  the  glazes  in  this  group  were  applied  to  porcelain 
bisque  vases.  In  all  cases  where  the  glazes  did  not  flow  ex- 
cessively or  where  crystallization  appeared,  the  red-violet  color 
was  prominent.  Where  excessive  flow  took  place  the  glaze 
remaining  on  the  surface  of  the  vase  was  a  clear  blue.  In  several 
cases  where  the  glaze  flowed  down  over  fire  clay  "buttons"  used 
as  setters,  the  color  of  the  glaze  on  these  buttons  was  a  dark 
green.  The  best  glazes  in  the  group  are  H3.E4,  E5,  F 3,  F4,  F5, 
G  3 ,  G  4  and  G  5 .  Member  F  4  appeared  to  be  the  best  one  in  all 
three  burns. 

Third  Group. — A  third  group  was  made  in  order  to  obtain 
lighter  shades  of  the  red-violet  color.  Since  F  4  seemed  to  hold 
the  color  so  persistently  and  showed  a  fair  range  of  temperature, 
it  was  selected  as  the  starting  point.  Lighter  shades  can  be 
produced  by  blending  F  4  with  a  similar  glaze  but  containing 
no  cobalt  oxide.  The  first  problem  to  solve  was  to  produce  such 
a  glaze  having  the  same  heat  range  and  fusibility  as  F  4.  In 
order  to  save  time  it  was  decided  to  make  a  triaxial  group  (Chart 


Purple  Produced  by  Use  of  Cobalt 

0.2  Na2  O  1        G-5  at  cone  0  2 
0.6  Mg  O  \    1 .4  B2  03       1  Si  02 
0.2  Co   O 


COBALT  COLORS  OTHER  THAN  HLUE.  13 


^^^^^\^r>rmi 


7)  by  placing  F  4  at  the  upper  apex,  and  the  two  following  color- 
less glazes  at  the  lower  corners: 

0.2  Na,0    )  _  ^  „._.  0.5  Na„0    )  _.  n  _._ 

„  „  '       >   1.5  B„0,  0.75  SiO,  °  .T  "       \  o.q  B,0,    0.75  SiO, 

o .  8  MgO     )       °     2    ■'        /0         "  0.5  MgO     )       v     2    J        '  ° 

The  only  constant  member  in  the  group  is  Si02  at  0.75 
molecule. 

The  group  was  made  by  fritting  the  three  extremes  and 
blending  as  was  done  in  the  two  preceding  groups.  Glazes  were 
applied  to  porcelain  discs  and  burned  to  cone  02. 

Examination  of  the  trials  indicates  that  there  is  no  difference 
in  shade  or  intensity  of  color  from  a  content  of  0.1  CoO  to  0.2 
CoO.  The  glaze  near  the  lower  left  corner  is  a  dark  lavender 
while  the  one  near  the  lower  right  corner  is  clear  blue.  As  the 
MgO  and  B,03  decrease  and  Na,0  increases,  the  color  tends 
toward  blue.  Wherever  crystallization  appears,  the  red- violet 
or  a  lighter  shade  tending  toward  lavender  appears. 


14  COBALT   COLORS   OTHER  THAN   BLUE. 

CONCLUSIONS. 

The  color  violet  is  composed  of  equal  intensities  of  red  and 
blue.  Most  of  the  colors  produced  in  the  foregoing  work  lie  be- 
tween the  violet  and  the  red.  A  fusion  of  either  soda  or  boric 
oxide  and  cobalt  oxide  gives  blue.  Cobalt  silicate  is  blue.  A 
mixture  of  magnesia  and  cobalt  oxide  heated  to  redness  gives 
pink.  The  color  darkens  tending  toward  red  as  the  temperature 
of  calcination  is  increased;  the  color  change,  however,  is  not  pro- 
nounced until  very  high  temperatures  are  reached. 

The  red-violet,  lavender  or  pink  color  is  apparently  due  to 
some  combination  of  magnesia  with  an  oxide  of  cobalt.  De- 
creasing MgO  or  increasing  Si02  causes  diminishing  red  and  in- 
creasing blue.  This  would  indicate  that  the  silica  has  broken 
up  the  magnesia-cobalt  combination,  thus  imparting  the  cobalt- 
silica  blue. 

Although  a  fusion  of  B203  and  CoO  gives  blue,  an  increase  in 
B203  in  the  foregoing  glazes  tends  toward  the  red  and  away  from 
the  blue,  indicating  that  the  magnesia-cobalt  red-violet  color 
is  not  only  stable  in  the  presence  of  B203  but  that  the  latter  en- 
courages the  red  by  some  action  not  definitely  understood. 

DISCUSSION. 

Mr.  Wilder:  I  would  like  to  ask  what  would  be  the  result 
of  increasing  the  heat  in  the  trials  shown  on  the  last  diagram? 

Mr.  St  nil:  You  would  tend  to  get  less  of  the  red-violet  or 
lavender  and  more  of  the  blue.  This  is  probably  due  to  the  fact 
that  the  glaze  becomes  very  fluid  as  the  temperature  increases 
and  attacks  the  body  vigorously.  The  alumina  taken  up  changes 
the  color  to  blue.  We  intend  to  continue  further  and  try  what 
we  call  an  insulating  glaze,  by  biscuiting  the  porcelain  at  05  to 
02,  then  applying  a  glaze  similar  to  the  first  one  on  the  board, 
as,  for  example : 

Uaa     1  *SiO.. 
rMgO     ) 

In  this  glaze  x,  y  and  z  must  necessarily  be  determined  experi- 
mentally in  order  to  fit  working  conditions.  After  applying  the 
insulating  glaze  to  the  soft  biscuit,  the  body  is  to  be  vitrified  at 
cone  u  or  cone  12,  then  the  colored  glaze  is  to  be  applied  and 


COBALT  COLORS  OTHER  THAN  BLUE.  1 5 

burned  to  maturity.  In  this  way  we  hope  to  exclude  alumina 
from  the  glaze. 

Mr.  Wilder:  I  would  like  to  ask  Professor  Stull  if  he  ever 
tried  to  make  pigments  by  calcining  the  magnesia? 

Mr.  Stull:     No,  I  have  never  done  that. 

Mr.  Landrum:  I  made  pigments  by  calcining  iron  oxide 
with  magnesia;  but  I  never  decided  whether  there  was  a  com- 
pound formed  or  not,  nor  whether  there  was  a  red-violet  color 
from  the  magnesia  and  the  ignition  simply  gave  a  more  homo- 
geneous pigment.  I  think  there  should  be  some  trials  made  by 
igniting  at  a  little  higher  temperature. 

Mr.  Stull:  If  the  color  so  obtained  were  stable,  it  would 
work  all  right,  but  apparently  these  colors  are  very  unstable 
during  fusion  in  the  presence  of  silica  and  alumina.  It  seems  to 
me  that  it  would  be  possible  to  make  over-glaze  colors  along  this 
line,  if  they  are  not  fired  too  high  and  thus  made  too  fluid.  The 
white  sample  in  the  right-hand  lower  corner  of  the  triaxial  is 
very  fusible  and  has  attacked  the  body  vigorously  as  it  is  pitted 
in  places.  Therefore,  the  over-glaze  colors  would  have  to  be 
fired  with  caution,  or  so  constituted  as  to  possess  a  wide  heat 
range. 

Mr.  Will:  I  make  blue  stains  of  various  composition  which 
in  cone  S  and  cone  10  fire  turn  out  a  pink-violet,  a  beautiful 
color,  but  the  invariable  experience  has  been  that  on  being  used 
as  colors  under  a  full  glaze  they  turn  to  a  deep  blue.  In  other 
words,  the  red  color  is  not  stable  except  with  a  matte  glaze. 
For  instance,  use  same  as  a  stain  for  a  matte  glaze,  or  a  semi- 
matte  underfired,  and  you  get  a  pink  glaze.  From  this,  purple 
glaze  is  often  produced  by  overfiring,  and  on  firing  to  a  gloss 
the  same  piece  will  show  a  blue  color. 

Mr.  Bruner:  I  would  like  to  ask  a  question  in  regard  to 
Chart  7.  Professor  Stull,  do  you  wish  to  give  us  the  impression 
that  in  the  lower  left-hand  corner,  the  effect  was  due  to  low 
soda,  high  magnesia,  high  boric  acid,  and  that  if  handled  cor- 
rectly, these  glazes  will  give  the  pink  color  and  on  the  other  hand 
with  low  magnesia  and  low  boric  acid,  the  blue  color  comes  out? 

Mr.  Stull:     That  is  right. 

Mr.  Bruner:     Are  all  those  pieces  exposed  to  just  about  the 


1 6  COBALT  COLORS  OTHER  THAN  BLUE. 

same  heat  or  would  you  say  their  color  was  due  to  their  position 
in  the  kiln?  You  do  not  mention  anything  about  the  fusibility 
and  the  possibility  of  the  glazes  being  much  more  fused  in  one 
end  of  the  kiln  and  the  fact  that  when  you  have  that  condition 
it  naturally  leaves  the  color  blue.  On  this  piece  (indicating 
number)  you  have  a  beautiful  red-violet,  as  you  call  it,  but  in- 
side it  is  blue.  Even  around  the  edges  here  you  can  see  a  little 
of  the  blue. 

Mr.  Stull:  Underneath  the  red-violet  glaze  there  is  a  thin 
film  of  blue  next  to  the  body,  and  where  the  glaze  is  thin  the  blue 
shows  through.  When  crystallization  takes  place  it  brings  out 
the  red-violet  color,  and  underfiring  also  brings  out  the  char- 
acteristic red-violet  color.  On  the  inside  of  the  piece,  the  thin 
glaze  has  attacked  the  body,  thus  giving  the  characteristic  cobalt- 
alumina  blue. 

Mr.  Will:  I  have  applied  one  of  these  reddish  blue  colors 
to  glazed  Belleek  ware  and  fired  it  again  at  glost  kiln  heat  (cone 
4-5)  and  there  also  one  could  not  help  noticing  the  phenomena  of 
crystallization  and  the  bringing  out  of  red  spots  where  under- 
fired,  while  the  balance  of  the  piece  showed  a  strong  deep  blue 
glaze  with  a  high  gloss. 

Mr.  Burt:  I  notice  a  number  of  these  samples  seem  to  show 
a  distinct  crystallization  wherever  the  pink  occurs,  and  I  wondered 
whether  Mr.  Stull  had  examined  it  with  that  in  mind.  You  get 
blue  on  the  inside,  but  on  the  outer  surface  where  you  have 
sufficient  surface  glaze,  you  produce  crystallization  phenomena 
which  develop  this  pink  crystal.  Is  not  the  color  something  of  a 
crystallization  phenomenon  ? 

Mr.  Stull:  It  is  true  that  the  crystals  do  show  the  color, 
but  the  red-violet  color  is  also  developed  in  an  underfired  glaze 
and  blue  in  an  overfired  glaze,  or  where  the  glaze  is  thin  and  has 
"fluxed  into  the  body."  On  Chart  1,  in  the  upper  left-hand 
corner  is  the  most  refractory  glaze  in  the  group.  It  is  as  soft  as 
chalk,  yet  it  shows  a  light  red- violet  color.  Alumina  and  cobalt 
together  at  a  red  heat  will  give  a  blue,  while  magnesia  and  cobalt 
will  give  pink.  I  do  not  know  whether  it  is  a  chemical  or  a 
physical  action  that  brings  out  the  blue  in  one  case  and  the  pink 
in  the  other. 


[Reprinted  from  Transactions  American  Ceramic  Society,     Vol.  XIV, 
by  Permission.] 


INFLUENCES  OF  VARIABLE  SILICA  AND  ALUMINA  ON 

PORCELAIN  GLAZES  OF  CONSTANT  RO. 

By  R.  T.  Stull,  Ceramic  Laboratories,  University  of  Illinois. 

INTRODUCTION. 

Porcelain   glazes   of   the   Seger   cone   formula   type   are   the 

most  inexpensive  to  produce  synthetically,  have  a  comparatively 

wide  range  of  maturing  temperature  and  give  but  few  defects. 

These  are  offered  as  the  principal  reasons  for  the  comparative 

meagerness  of  literature  pertaining  to  investigations  on  glazes 

of  this  type. 

Seger1  gives  the  following  as  glaze  formula  commonly  used 
for  porcelain: 

RO,  ( i  to  1.25)  ALA,,  (10  to  12)  Si02 
and  for  Seger  porcelain2 

RO,  0.5  A1,03,  (4  to  6)  Si02 
Prof.  Orton3  gives  the  following  limits  for  characteristic  porcelain 
glazes : 

0.1  too.5  K,0)  . ,  _  _._ 

n  n>  C°-5  to  I25  ALA,  4-0  to  12.5  SiO, 
0.9  to  0.5  CaO  j  z   *  02 

EXPERIMENTAL  WORK. 

In  a  study  of  porcelain  glazes4  of  the  cone  formula  type, 
two  groups  were  made  in  order  to  illustrate  the  influences  of 
variable  silica  and  alumina.     The  first  group  covered  the  limits 


_      -     V0.3  to  1.0  A1,03  [  i-S  to  7.2  SiO, 


and  comprised  eight  horizontal  series,  from  A  to  H,   containing 
eighty  glazes  in  all. 

The  glazes  in  that  portion  of  the  field  covered  by  the  A  to 
H  series  were  made  by  blending  the  four  extremes  according  to 
their  combining  weights.  The  formulae  and  batch  weights  of 
these  extremes  are: 


1  Vol.  II.    Translations  Seger,  p.  705. 

2  Ibid.,  p.  706. 

3  Glaze  lectures  at  Ohio  State  University,  1901-2 

4  W'jrk  done  by  classes  1911  and  1912,  University  of  Illinois. 


1 8         INFLUENCES  OF  SILICA  AND  ALUMINA  ON  PORCELAIN  GLAZES. 


O 

O 

d 

O 

d 
3 

d 

in 

2 

a 

« 

0 

d 

Clay 

0 
5 

Glaze 

■  6      do 

0 

= 

0 
O 

A-I 

A— 10 

0.3 

o-3 
0.3 
o-3 

O.7 
O.7 
O.7 

O.7 

0.3 
0.3 
1 .0 
1 .0 

1.8 

7-2 

1.8 
7.2 

167 . 1 
167 . 1 

167 . 1 
167 . 1 

70.0 
70.0 
70.0 
70.0 

yo.3 

90.3 

109.2 

324  0 

240.0 

H-i 

H-io 

Glazes  in  the  W  to  Z  series  were  also  made  in  the  same  manner 
with  the  exception  that  it  was  necessary  to  employ  a  frit  in 
order  to  introduce  the  excess  K20  which  could  not  be  furnished 
by  feldspar.  The  formulae  and  batch  weights  of  the  four  ex- 
tremes are: 


u 
3 

a 

£ 

O 

O 

O 

w 

■0 

O 
0 

0 

c 

W 

0 

< 

w 

to 

to 

0 

<! 

to 

w-02 

0-3 

0.7 

0.25 

0.6 

85.6 

50.0 

23-4 

W-6 

0.3 

0.7 

0.25 

4.8 

21.4 

125-3 

65.0 

198.0 

Z-02 

0.3 

0.7 

0. 10 

0.6 

85.6 

50.0 

Z-3 

0.3 

0.7 

0. 10 

30 

85.6 

50.0 

144.0 

Frit  for  the  above : 


o .  2  ALO,  1 . 2  SiOo 


Feldspar  =  1 1 1 . 4 
K2C03  =  552 
CaC03       =     40.0 


o .  6  K20 
o .  4  CaO 
Comb.  wt.  =  171 .2 

Crazing  is  comparatively  rare  in  this  type  of  porcelain  glaze, 
due  to  the  vitreous  nature  of  the  body  and  the  similarity  in  compo- 
sition of  body  and  glaze.  In  order  to  intensify  crazing  and  to 
locate  that  portion  of  the  field  in  which  it  would  be  most  likely  to 
occur,  the  glazes  were  applied  to  porous,  biscuit  wall  tile,  which 
shrunk  considerably  but  were  still  porous  at  the  end  of  the  burn. 

The  glazes  were  applied  a  little  thicker  than  is  customary 
in  practice,  and  the  trials  set  in  tile  saggers  and  burned  to  cone 
11  in  36  hours.  The  results  are  shown  graphically  in  Charts 
I  and  II. 

DISCUSSION  OF  RESULTS. 

On  Chart  1,  the  molecular  variations  of  silica  are  plotted 
alone:  the  abscissa  and  the  molecular  variations  of  alumina  alonar 


INFLUENCES  OF  SILICA  AND  ALUMINA  I  ).\  PORCELAIN  GLAZES.        I  9 

the  ordinate.     The  letters  at  the  left  denote  the  horizontal  series 


TRAXS.  AM.  CER.  SOC.  VOL.  XIV 


CHART  1 


STULL 


^7" 


0.6      /.2      /&      2<4-    *3-0    3.6     4-2     4&    S.4-    6.0     S6    7.2. 

and  the  numbers  along  the  top  the  vertical  series,  so  that  each 
glaze  is  located  by  a  letter  and  a  number. 

\o.\  K,0) 
Since  the  RO  for  all  glazes  is  constant,  the  formula 

1 0.7  CaOj 
of  any  glaze  can  be  read  from  the  chart  by  referring  to  the  ordi- 
nate  for   its   alumina  and   to   the   abscissa  for   the   silica.     For 

ro.3  K2Oi 
example,    the   formula   of   E-5    is  j  0.7  A1203  4.2  Si02. 

(0.7  CaOj 
The  alumina  is  constant  in  a  horizontal  series  while  the  silica 
varies.     In  a  vertical  series  the  silica  is  constant  and  the  alumina 
is  the  variable. 

To  the  left  of  the  line  M    T    are  the  underfired  mattes,    and 


20        INFLUENCES  OF  SILICA  AND  ALUMINA  ON  PORCELAIN  GLAZES. 

between  M  J  and  N  U  are  the  matured  mattes.  Between 
N  U  and  X  K  are  mattes  showing  a  sheen  or  slight  gloss  and 
designated  as  semi-mattes.  The  bright  glazes  occur  between 
N  K  and  O  S,  and  below  O  S  the  glazes  are  devi trifled.  The 
glazes  are  all  crazes  below  the  line  IPRL  and  all  sound  above 
this  line.  The  dotted  line  O  T  passes  through  highest  gloss 
of  each  series. 

Beginning  at  the  ordinate  on  Chart  i  and  moving  to  the  right 
parallel  to  the  abscissa,  it  is  observed  that  crazing  and  matte 
texture  decrease  with  increase  in  silica,  and  that  brilliancy  in- 
creases up  to  the  axis  of  highest  gloss,  Q  T,  beyond  which  brilliancy 
decreases,  crazing  increases  and  finally  devitrification  occurs. 

Moving  from  the  abscissa  upward  parallel  to  the  ordinate, 
we  see  that  increasing  alumina  has  decreased  crazing  of  glazes 
both  high  and  low  in  silica,  has  decreased  devitrification  in  high 
silica  glazes,  and  increased  matteness  in  low  silica  members. 

A  comparison  of  the  influences  of  variable  A1203  with  those 
of  variable  B203  is  of  interest.  It  has  been  shown5  that  increasing 
B203  decreases  devitrification  and  crazing  in  high  silica  glazes 
and  increases  crazing  and  decreases  matte  texture  in  low  silica 
glazes.  B203  and  A1203  then  function  the  same  in  high  silica 
glazes  but  function  oppositely  in  low  silica  glazes. 

In  Chart  2,  the  glazes  are  located  by  the  molecular  ratios 
of  silica  to  alumina  on  the  abscissa  and  by  the  total  oxygen  ratios 
on  the  ordinate.  The  molecular  ratio  of  silica  to  alumina  is 
independent  of  the  total  oxygen  ratio,  but  the  total  oxygen  ratio 
is  partly  dependent  upon  the  silica-alumina  ratio.  Therefore, 
in  plotting  glaze  groups  similar  to  Chart  2,  the  evidence  pre- 
sented is  influenced  by  one  dependent  and  one  independent 
variable.  This  must  be  borne  in  mind  in  drawing  conclusions, 
otherwise  they  may  be  misleading. 

The  underfired  mattes  occur  at  1,  crazed  mattes  at  2,  sound 
mattes  at  3,  semi-mattes  at  4,  crazed  brights  at  5,  sound  brights 
at  6,  and  glazes  which  are  crazed  and  devitrified  at  7.  The  line 
A  B  is  the  high  gloss  axis. 


5  "Opalescence  and  the  Function  of  B203  in  the  Glaze,"  Trans.  A.  C  S.,  Vol.    12,   pp. 
119  to  137. 


INFLUENCES  OF  SILICA  AND  ALUMINA  ON  PORCELAIN  GLAZES.         2  1 


*       §      5       ^      & 

(^       N.      K      v<i      Ki 


^     ^     Nf    i 


^     5     J    Q 


<\j     tVi      s      s     Q 


22        INFLUENCES  OF  SILICA  AND  ALUMINA  ON  PORCELAIN  GLAZES. 


The  chart  shows  graphically  that  the  matte  glazes  fall  within 
narrow  limits  and  that  the  bright  glazes  occur  within  wide  limits. 
In  the  following  table  is  given  the  ratio  limits  within  which  the 
different  kinds  occur : 


i.  Underfired  matte  glazes  (at  cone  n) . 

2.  Crazed  matte  glazes  (at  cone  n) 

3.  Sound  glazes  (at  cone  11) 

4.  Semi-matte  glazes  (at  cone  11) 

5.  Crazed  bright  glazes  (at  cone  11) 

6.  Sound  bright  glazes  (at  cone  n) 

7.  Crazed  devitrified  glazes  (at  cone  11). 


S1O2 :  AI2O3 

1.7-  2.7 

2.4-  6.0 
3.0-  4.0 
4.0-  5.0 
6.0-24.0 
51-130 
12 .0-30.0 


The  trials  show  that  the  best  bright  glazes  are  found  be- 
tween oxygen  ratios  of  2.5  and  3.6  and  silica-alumina  ratios  of 
7  and  8.2.  The  best  mattes  occur  between  O.  R.'s  of  1.5  and  1.8 
and  silica-alumina  ratios  of  3.2  and  3.8.  The  high  fire  matte 
glazes  given  by  Prof.  Binns6  fall  within  these  limits. 

As  the  alumina  increases,  the  positions  of  the  glazes  ap- 
proach the  line  passing  through  C  to  the  origin  O.  This  line 
represents  a  series  of  glazes  having  constant  alumina,  and  variable 
silica.  The  general  formula  which  satisfies  any  member  in  this 
series  is  RO  00  A1203,  z  Si02  in  which  z  may  vary  from  o  to  00 . 
When  z  becomes  infinitely  large  the  formula  may  be  reduced 
to  the  simple  one  of  1  A1203,  y  Si02.  Dehydrated  kaolinite,  having 
a  total  oxygen  ratio  of  1.3V3  and  a  molecular  ratio  of  2,  is 
located  on  the  line  O  C  at  D. 

The  line  O  C  is  the  dividing  line  between  possible  and  im- 
possible glazes.  Take  any  point  to  the  left  of  this  line,  as  point 
E  located  by  an  oxygen  ratio  of  5  and  a  silica-alumina  ratio  of 
5.  From  the  general  formula  of  the  glaze  1  RO,  rcAl203,  y  Si02, 
the  following  equations  are  obtained : 


2y 
i~^3x  =  5 
in  which  x  =  — 1   and  y  =  — 5. 
to  be  located  at  E  must  be  RO,  - 
possible    except    mathematically. 


^=5 

X 

The  formula  then  of  a  glaze 

-1  A1203,  — 5  Si02  which  is  im- 

In    the    same    manner,    any 


6  Trans.  A.  C  S.,  Vol.  VII,  pp.  115-121. 


INFLUENCES  OF  SILICA  AND  ALUMINA  ON  PORCELAIN  GLAZES.        23 

other  point  to  the  left  of  O  C  may  be  shown  to  represent  a  glaze 
of  the  general  formula  1  RO,  x  A1,03,  y  Si02,  in  which  x  and  y 
are  negative. 

As  the  dividing  lines  between  the  different  glazes  on  Chart 
II  approach  the  line  O  C,  they  curve  upward,  indicating  that  the 
higher  the  molecular  content  of  alumina  in  the  glaze  the  higher 
is  the  oxygen  ratio  for  sound  matte  and  bright  glazes  and  that 
devitrification  appears  at  a  higher  total  oxygen  ratio  in  high 
alumina  glazes  than  it  does  in  glazes  lower  in  alumina. 

The  foregoing  work  seems  to  indicate  that  it  is  necessary 
to  employ  higher  oxygen  ratios  for  high  alumina  glazes  (both 
bright  and  matte)  than  it  is  for  low  alumina  glazes,  and  that  the 
total  oxygen  ratio  of  1  :  2  so  often  referred  to  as  being  best  for 
bright  glazes  does  not  hold  with,  perhaps,  the  exception  of  low 
alumina  glazes  maturing  at  lower  temperatures. 

DISCUSSION  WRITTEN  AFTER  READING  THE  ABOVE  PAPER. 

Mr.  Staley:  This  paper  is  a  fine  example  of  careful  and 
systematic  work  and  of  concise  and  graphic  presentation  of 
data.  So  well  has  the  work  been  done  that  there  is  little  room 
for  discussion  or  comment. 

From  the  standpoint  of  practical  porcelain  glazes,  the  first 
series,  the  A,  B,  C  series,  is  of  most  interest.  This  may  be  divided 
into  two  groups  of  glazes:  first,  a  group  that  can  be  made  from 
the  ordinary  potter's  materials,  feldspar,  whiting,  clay  and  Hint; 
and  second,  a  group  in  which  it  is  necessary  to  use  Al(OH)3, 
or  its  equivalent.  The  line  dividing  these  two  groups  in  Chart 
1  runs  in  a  straight  course  from  the  glaze  with  0.3  A1203  and 
1.8  SiO,  to  a  point  that  would  indicate  a  glaze  with  1.0  A1203 
and  3.2  Si02.  It  is  plainly  evident  from  the  chart  that  the  large 
majority  of  the  glazes  in  the  first  group  are  good  bright  glazes 
at  cone  1 1 . 

Inasmuch  as  Prof.  Stull,  for  the  sake  of  simplicity  in  blending, 
introduced  considerable  amounts  of  Al(OH).,  into  the  high  alumina 
glazes  of  the  first  group,  we  feel  justified  in  predicting  that  if 
all  the  members  of  this  group  had  been  made  from  the  materials 
ordinarily  used  by  the  potters,  the  boundaries  of  the  matte  and 
semi-matte  areas  would  have  been  shifted  somewhat  toward  the 


24        INFLUENCES  OF  SILICA  AND  ALUMINA  ON  PORCELAIN  GLAZES. 

upper  left-hand  corner  of  the  chart.  We  base  this  prediction 
on  the  well  known  fact  that  in  high  alumina  glazes  the  intro- 
duction of  a  given  amount  of  alumina  as  the  free  oxide,  or  its 
equivalent,  has  a  more  decided  tendency  to  produce  matteness 
than  the  introduction  of  an  equal  amount  of  alumina  as  clay. 

Professor  Stull  has  shown  beautifully  the  facts  that  under 
certain  conditions  increase  of  alumina  can  stop  crazing  and  in- 
crease of  Si02  can  cause  crazing.  Of  course,  both  these  state- 
ments are  contrary  to  Seger. 

The  close  relation  between  the  boundary  lines  for  crazing 
and  devitrification  in  high  silica  glazes  obviously  suggests  that 
the  strains  set  up  in  the  process  of  devitrification  are  responsible 
for  the  crazing.  This  is  simply  one  more  instance  of  crazing  not 
caused  by  difference  in  coefficient  of  contraction 

Inspection  of  the  chart  shows  that  a  very  simple  rule  can 
be  devised  for  making  a  long  series  of  good  bright  or  matte  por- 
celain glazes  with  this  RO.  Any  raw  glaze  should  have  at  least 
0.05  equivalent  of  clay  for  mechanical  reasons,  so  we  will  start 
with  0.35  A1203  and  2.40  Si02.  Now  by  adding  A1203  and  SiO, 
to  this  glaze  in  the  proportion  of  o.  10  equivalent  of  A1203  to 
0.8  equivalent  of  Si02,  we  can  make  a  long  series  of  glazes  lying 
close  to  the  line  of  best  bright  glazes  free  from  crazing.  In  terms 
of  batch  weights,  this  means  that  we  can  start  with  a  glaze  of 
the  following  batch:  33  feldspar,  14  whiting,  21  / 2clay  and  6  flint. 
To  this  batch  we  add  clay  and  flint  in  the  proportion  of  1  part 
clay  to  1.4  parts  flint.  To  get  the  longest  possible  series  of  mattes, 
we  simply  drop  out  the  flint  from  the  above  base  glaze  and  make 
successive  additions  of  clay.  The  members  lowest  in  clay  of  this 
series  would  be  liable  to  craze. 

Mr.  Stull:  It  seems  to  be  a  question  as  to  whether  all  of 
the  glaze  ingredients  go  into  solution  or  not.  If  complete  solu- 
tion takes  place,  the  difference  in  texture  of  a  glaze  is  not  so 
marked  whether  the  alumina  has  been  added  as  Al2(OH)e  or 
introduced  as  clay.  However,  a  high  alumina  content  tends 
to  increase  viscosity  which  operates  against  diffusion  and  con- 
sequent homogeneity. 

Although  these  matte  glazes  contain  some  alumina  introduced 
as  the  hydroxide,  the  trials  showed  that  the  best  mattes  occurred 


INFLUENCES  OF  SILICA  AND  ALUMINA  ON  PORCELAIN  GLAZES.        25 

between  the  O.R.'s  of  1.5  and  i.S  as  has  been  referred  to.  The 
high  temperature  matte  glazes  reported  by  Professor  Binns  in 
Volume  YII  fall  within  these  limits.  He  reports  his  best  matte 
as  having  an  O.  R.  of  1.69.  Although  he  used  the  regular  potter's 
materials  and  fired  at  cones  8  and  9,  it  must  be  borne  in  mind 
that  the  replacement  of  clay  by  aluminum  hydroxide  and  Hint 
raises  the  maturing  temperature  Therefore,  Prof.  Staley  is 
correct  in  his  prediction,  though  it  is  probable  that  the  lines 
would  have  been  shifted  only  a  short  distance. 

The  fact  that  increase  in  alumina  tends  to  overcome  crazing 
was,  to  my  knowledge,  first  brought  out  by  Purdy  and  Fox  in  their 
work  on  "Fritted  Glazes." 

A  study  of  results  plotted  graphically  frequently  reveals 
far  more  than  mere  description  can  do.  In  going  back  to  the 
charts,  a  point  is  observed  which  might  be  of  interest  to  the  glass 
manufacturer.  On  Chart  2  it  is  observed  that  devitrification 
occurs  at  higher  oxygen  ratios  as  the  alumina  increases.  Since 
sand  is  the  cheapest  material  in  the  glass  batch,  there  is  an  ad- 
vantage in  using  all  the  sand  that  practice  will  permit  for  common 
window  and  bottle  glasses. 

Frequently  the  manufacturer  of  the  common  grades  of  glass 
is  limited  in  the  amount  of  sand  he  can  use,  owing  to  the  liability 
of  the  glass  to  devitrify.  If  alumina  can  be  introduced  or  its 
quantity  increased  in  the  glass,  a  larger  per  cent,  of  sand  can  be 
employed.  Not  only  will  the  alumina  tend  to  prevent  devitri- 
fication, but  will  also  tend  to  counteract  increased  viscosity  due 
to  increased  silica.  The  fusion  temperature  then  would  be  the 
principal  limiting  factor. 


[Reprinted  from  Transactions  AMERICAN  Ceramic  Society,     Vol.  XIV, 
liv  Permission.] 

INVESTIGATIONS  ON  THE  DIELECTRIC  STRENGTH  OF 
SOME  PORCELAINS.1 

By  B.  S.  Radcuffe,  Van  Asselt,  Wash. 
In   the   following  work   on  porcelains,   four   problems   were 
investigated  for  the  purposes  of  determining: 

i.  The  relation  between  dielectric  strength  and  thickness. 

2.  The  effect  upon  dielectric  strength  due  to  varied  heat 
treatment  during  burning  and  cooling. 

3.  The  value  of  fire  clays  as  raw  materials  for  high  tension 
insulators. 

4.  Influence  of  lime  on  dielectric  strength. 

INFLUENCE  OF  THICKNESS. 

The  dielectric  strengths  of  nearly  all  insulating  materials 
(porcelain  included)  are  considered  proportional  to  the  thickness. 
The  strengths  of  varnished  and  impregnated  paper  insulators 
are  exceptions.  Since  no  experimental  data  was  found  pertaining 
to  the  relative  dielectric  strength  to  the  thickness  of  porcelains, 
it  was  deemed  advisable  to  make  a  few  simple  practical  tests  in 
order  to  determine  this  point  for  use  in  the  work  following.  For 
this  purpose,  a  body  having  the  following  composition,  which 
vitrifies  at  cone  12,  was  made:  Tenn.  ball  clay,  No.  1,  15;  No. 
Carolina  kaolin,  20;  Eng.  china  clay,  25;  spar  (Brandywine 
Summit),  20;  flint  (Ohio,  8  hr.  grind),  20. 

The  body  was  prepared  in  the  usual  manner  according  to 
factory  practice  and  the  trials  jiggered  in  the  form  of  small 
crocks  (Fig.  1)  which  could  be  nested  closely  so  that  all  pieces 
would  receive  the  same  heat  treatment. 

The  trials  were  made  in  different  thicknesses,  varying  from 
1.4  mm.  to  7  mm.,  by  adjusting  the  jigger  tool.  The  trials  were 
burned  to  cone  i21j2  and  punctured  under  transformer  oil  (Fig.  2), 
the  voltage  being  increased  gradually  by  a  rheostat.  As  soon 
as  the  trial  was  punctured,  the  current  was  immediately  broken. 

The  thickness  at  the  point  of  puncture  was  measured  by 
a  micrometer.  Five  to  ten  trials  made  of  the  same  thickness 
were  punctured  in  each  case.     Whenever  puncture  took  place 


1  An  abstract  of  work  done  in  1909-10  in  partial  fulfilment  of   requirements  for  M.  S. 
■degree  in  Ceramics  at  the  University  of  Illinois,  under  supervision  of  R.  T.  Stull. 


28 


DIELECTRIC    STRENGTH    OF    PORCELAINS. 


r/e./ 


frADCL/FFE 


PEr^/LS  OF 


through  a  flaw,  the  trial  was  rejected.  The  voltages  required 
for  puncturing  sound  trials  of  the  same  thickness  were  averaged, 
the  thickness  being  plotted  on  the  ordinate  and  voltage  on  the 
abscissa  (Fig.  3). 


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Calculating  the  average  puncture  voltage  per  mm.  thick- 
ness for  all  trials  tested,  assuming  that  the  puncture  voltage 
is  directly  proportional  to  the  thickness,  gives  a  voltage  of  14,525. 
This  point  is  plotted  and  the  heavy  dotted  straight  line  passes 


DIELECTRIC   STRENGTH    OF    PORCELAINS. 


29 


from  the  origin  through  it.  Owing  to  the  fact  that  a  voltage 
higher  than  100,000  was  not  available,  pieces  over  6l/2  mm. 
in  thickness  could  not  be  tested.  However,  the  limits  covered 
exceeded  the  requirements  in  the  future  tests. 

Some  interesting  results  were  obtained  by  puncturing  the 
same  test  piece  repeatedly  in  the  same  spot.  One  piece,  5.7  mm. 
in  thickness  required  83,800  volts,  and  was  given  a  second  test  and 
punctured  at  79,000  volts,  a  third  test  required  59,300,  a  fourth 
51,200.  When  the  trial  was  shifted  to  a  new  place,  the  voltage 
required  to  puncture  it  was  77,500.  Other  trials  were  treated 
in  the  same  manner  giving  similar  results.  Repeated  tests 
through  the  same  line  of  puncture  weakened  the  dielectric  strength 
at  that  point,  but  not  until  several  punctures  did  the  porcelain 
become  too  weak  to  resist  a  fairly  high  voltage. 

Apparently  the  current  fuses  the  porcelain  in  passing.  Upon 
breaking  several  pieces  through  the  line  of  puncture  a  glassy 
appearance  was  always  noticeable. 

INFLUENCE  OF  VARIABLE  HEAT  TREATMENT. 

There  seems  to  be  no  data  available  pertaining  to  the  effect 
of  rate  of  burning  and  cooling  upon  the  dielectric  strength  of 
porcelains.  In  order  to  throw  some  light  upon  this  subject, 
four  porcelain  bodies  were  selected  from  the  work  of  Bleininger 
and  Stull  on  "The  Yitrifi cation  Range  and  Dielectric  Strength 
of  Some  Porcelains."  These  bodies  are  here  designated  by  A, 
B,  C  and  D.     Besides  these,  E  was  made  by  blending  the  four. 


Body                  Georgia          Term.          X.  Car 
kaolin       ball   Xo.  1        kaolin 

Eng.   China       Potash            Ohio 
clay   No.  7        feldspar          flint 

A 50 

B | 

C | 

D | 

E |         5 

55 

55 

0               27 

40                  10 

15                  30 

25                  20 

60                    20                  20 

IS                   23                 18 

Five  more  bodies  were  made  similar  to  these  except  that 
soda  feldspar  replaced  the  potash  feldspar  by  theoretical  mole- 
cules.    These  bodies  are  designated  as  Ai,  Bi,  Ci,  Di,  and  Ei. 

Twenty  trials  were  made  from  each  of  the  ten  bodies.     These 


3Q 


DIELECTRIC    STRENGTH    OF    PORCELAINS. 


trials  were  divided  into  four  sets,  each  set  containing  five  trials 
made  from  each  body.  Each  set  was  burned  and  cooled  under 
different  conditions.  Set  i  was  burned  to  cone  10  in  six  hours 
and  cooled  slowly  in  order  to  determine  the  effect  of  quick  firing 
and  slow  cooling.  Set  2  was  burned  to  cone  13  in  six  hours  after 
which  air  was  passed  through  the  kiln  cooling  the  temperature 
down  to  cone  02  in  one  hour.  The  kiln  was  then  allowed  to 
cool  slowly.  Set  3  was  burned  to  cone  10  in  six  hours  then  the 
temperature  was  gradually  raised  to  cone  12  in  an  additional 
14  hours,  then  carried  rapidly  to  cone  17  and  held  for  2  hours. 
The  kiln  was  then  allowed  to  cool  slowly.  Set  4  was  burned  to 
cone  10  in  6  hours,  gradually  raised  to  cone  13  in  an  additional 
18  hours  and  held  for  20  hours.  The  kiln  was  then  cooled  down 
to  cone  2  in  five  hours,  then  allowed  to  cool  slowly. 

C  and  Ci  in  the  first  burn  showed  2  per  cent,  porosity  but 
all  the  other  bodies  were  well  vitrified. 

AVERAGE  VOLTAGE  PER  MM.  REQUIRED  TO  PUNCTURE  TRIALS. 


Body 

Part  1, 
Cone  10 

Part  2, 
Cone  13 

Part  3, 
Cone  17 

Part  4. 
Cone  13 

A 

Ai 

B 

Bi 

C 

Ci 

D 

D, 

E 

Ei 

13260 
12840 
134OO 
14000 
IO32O 
9180 
14540 
13400 
!355Q 
13560 

13 1  20 
13100 
13COO 
13640 
13960 
13220 
1 3 150 
13920 
13470 
14820 

12600 
14300 
13500 
13620 
12760 
13820 
13680 
I  3  ICO 

1466 ) 
14100 

13070 
13870 
13000 
14160 
1 3 1 80 
13860 
14100 
135^0 
12850 
13860 

The  tests  show  that  there  is  not  a  very  wide  difference 
in  the  dielectric  strengths  of  the  different  bodies  or  in  the  manner 
of  heat  treatment.  By  taking  the  average  puncture  voltage 
per  mm.  for  each  different  body  for  the  four  different  burns 
(excluding  C  and  Ci  which  were  porous  in  the  first  burn),  we  have 
the  following  table  which  shows  that  the  soda  feldspar  bodies 
have  higher  dielectric  strengths  than  the  corresponding  potash 
feldspar  bodies  in  all  cases  except  in  bodies  D  and  Di  in  which 
case  D  shows  a  higher  dielectric  strength  than  Di. 


DIELECTRIC    STRENGTH    OF    PORCIvLAIXS. 


31 


Potash 

Average 

Average 

Soda 

spar 

voltage 

voltage 

spar 

bodies 

per  mm. 

per  mm. 

bodies 

A 

'.!"!- 

'33  27 

A-i 

B 

13225 

13855 

B-i 

c 

13300 

13633 

C-i 

D 

13867 

13485 

D-i 

E 

13632 

14185 

E  1 

In  order  to  get  a  comparison  of  the  effects  of  variation 
in  heat  treatment,  the  average  voltage  per  mm.  is  taken  of  the 
ten  bodies  for  each  of  the  four  different  burns.  In  averaging 
the  first  burn,  bodies  C  and  Ci  are  rejected  on  account  of  their 
porosities.  The  percentage  variation  between  maximum  and 
minimum  puncutre  voltages  is  less  than  0.55  per  cent,  showing 
that  the  dielectric  strength  was  substantially  unaffected  by  the 
variations  in  burning  and  cooling  from  cone  10  to  cone  17. 


Burn 

Cone 

Average   puncture 
voltage  per  mm. 

Part       I 

Part     II 

Part  III 

IO 
13 
17 
13 

13569 

13540 
I  3614 

Part  IV 

i  S547 

FIRE  CLAYS  AS  RAW  MATERIALS  FOR  HIGH  TENSION  INSULATORS. 

The  trade  demands  a  white  porcelain  body  for  high  tension 
insulators.  Frequently  a  dark  colored  glaze  (usually  brown) 
is  called  for.  If  a  colored  body  could  be  employed  containing 
a  high  per  cent,  of  fire  clay,  a  cheaper  body  and  a  more  uniform 
color  of  glaze  would  be  the  result.  Insulators  made  from  No.  2 
fire  clay  or  stoneware  clay  do  not  show  a  high  dielectric  strength. 
These  clays  vitrify  at  or  near  cone  8  while  the  white  high  tension 
porcelain  insulators  vitrify  around  cone  12. 

In  order  to  obtain  bodies  which  would  vitrify  near  cone  12, 
three  fire  clays  were  blended  triaxially  (Fig.  4).  The  three  fire 
clays  selected  were:  Olive  Hill  flint  fire  clay  (calcined);  Olive 
Hill  Xo.  1  plastic  fire  clay;  Bloomingdale2  No.  2  plastic  fire  clay. 


2  An  excellent  stoneware  clay,  vitrifying  at  cone  8. 


32  DIELECTRIC    STRENGTH    OF    PORCELAINS. 

rt?ANS  AM  C£f?  SOC  VOL  X/\s  F/&  ■>£  RADCUFFE 

JOO-FL/A/rCt-Ar 


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Five  trials  of  each  body  were  made  and  burned  to  cone  i21/2.. 
The  porosities  and  puncture  voltages  were  determined  and  aver- 
aged. These  results  are  plotted  on  the  triaxial  diagram  (Fig.  5), 
the  dotted  lines  representing  porosities  and  the  heavy  solid 
lines  puncture  voltages  per  millimeter  thickness. 

The  results  show  that  90  parts  No.  1  plastic  fire  clay  and 
10  parts  calcined  flint  fire  clay  give  a  body  of  the  highest  dielec- 
tric strength  at  cone  i21/2,  and  even  though  this  body  had  1  per 
cent,  porosity,  it  compares  very  favorably  with  the  best  white 
porcelains  in  strength,  14,000  volts  per  mm.  being  required  to 
puncture  it. 

When  No.  2  fire  clay  or  stoneware  clay  replaces  the  No.  1 
plastic  clay,  the  flint  clay  remaining  constant,  the  dielectric 
strength  is  lowered  even  though  the  porosity  is  lowered  at  the 
same  time. 

Bodies  containing  50  per  cent,  or  more  of  No.  2  clay  showed 
evidences  of  a  "bleb"  structure,  which  weakened  them,  causing 
them  to  puncture  at  a  low  voltage.  The  substitution  of  10  per 
cent.  No.  2  clay  for  No.  1  in  body  31,  which  gives  body  No.  32., 


DIELECTRIC    STRENGTH    <  >F    PORCELAIN'S. 


7~/Z4jVS  AWOW  SOC.  M/.  X/IS 


/PPLAT/l/E  PO/?05/7/£S AV/P 

r/&E:C£AY'ML>(rC//i'£S 
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33 


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did  not  materially  lower  the  porosity,  yet  it  lowered  the  puncture 
voltage  from  14,000  to  12,500. 

Trials  which  were  subsequently  made  from  bodies  14,  22 
and  31  and  burned  to  cone  14  gave  a  porosity  for  14  of  1.34 
and  a  puncture  voltage  of  13,600  per  mm.  The  porosity  of  No.  22 
was  0.08  and  its  puncture  voltage  14,100  per  mm.  Porosity 
of  No.  31  was  zero  and  its  puncture  voltage  14,600,  an  increase 
in  voltage  of  600  for  a  decrease  in  porosity  of  1  per  cent.  The 
white  porcelain  body  of  highest  dielectric  strength  found  in  the 
foregoing  work  is  the  soda  feldspar  body  Ei,  giving  a  puncture 
voltage  of  14,820  per  mm.  in  the  part  II  burn.  The  potash  feld- 
spar body  of  highest  dielectric  strength  is  D,  showing  a  puncture 
voltage  of  14,660  in  the  part  III  burn. 

In  so  far  as  dielectric  strength  is  concerned,  the  foregoing 


34 


DIELECTRIC    STRENGTH    OF    PORCELAINS. 


evidence  indicates  that  vitrified  bodies  made  from  refractory 
fire  clays  stand  on  an  equal  footing  with  white  porcelains  for  high 
tension  insulators. 

Good  colored  high  tension  insulators  can  be  made  from  a  body 
composed  of  No.  i  plastic  fire  clay  (part  of  which  may  be  calcined) 
and  a  small  amount  of  feldspar  to  assist  vitrification.  The  use 
of  flint  fire  clay  in  the  body  lowers  the  dielectric  strength  by 
increasing  porosity  through  its  refractoriness.  The  plasticity, 
working  properties  and  shrinkage  of  a  fire  clay  body  can  be  con- 
trolled much  better  than  white  bodies  and  at  the  same  time,  it 
would  be  cheaper  in  composition. 

INFLUENCE  OF  LIME  ON  DIELECTRIC  STRENGTH. 

In  order  to  determine  the  effect  of  lime  upon  the  dielectric 
strength  of  porcelain,  the  following  bodies  were  made  in  which 
CaC03  was  used  to  vitrify  the  bodies  in  place  of  feldspar.  Part 
of  the  clay  was  calcined  in  order  to  control  working  properties. 
The  trials  were  burned  to  cone  14  and  porosities  and  puncture 
voltages  determined.  These  results  are  given  in  the  following 
table. 


Body 


Tenn. 
ball  C 
No.  1 


N.  Car. 
kaolin 


Ohio 
flint 


Calcined 

N.  Car. 
kaolin 


CaCQ3 


F.  . 
Fl. 
F2. 

F3. 

F4- 
F5- 
F6. 

F?. 
F8. 


10 
10 


10 
10 


45 
45 
45 
45 
45 
45 
45 
45 
45 


23 


20 

19 
18 

17 
16 

15 


The  results  show  that  6  per  cent.  CaC03  has  produced  a  non- 
porous  body  at  this  temperature  which  does  not  show  a  high 
dielectric  strength,  and  that  each  increase  in  CaO  has  increased 
the  dielectric  strength.  F5  containing  5  per  cent.  CaC03  has 
a  porosity  of  12.84  per  cent.  F6  shows  that  an  increase  of  1 
per  cent,  of  CaC03  has  lowered  the  porosity  to  almost  zero. 


DIELECTRIC   STRENGTH   OF    PORCELAINS. 


35 


Body 


Per  cent, 
porosity 


Average 
voltage 
per  mm. 


Body 


Per  cent 
porosity- 


Average 
voltage 
per  mm. 


F. 

Fi. 

Fa. 

F3 


28.02 
27.60 

20.52 


F4- 
F5- 
F6. 

F7. 

F8. 


12.65 

12.84 

0.05 

0.03 

0.06 


5000 
6000 
6700 
8000 


When  the  puncture  tests  of  F6,  F7  and  F8  are  compared 
to  those  of  feldspar  porcelains  of  the  same  porosities  and  burned 
at  the  same  temperature  or  even  a  little  lower,  it  is  observed  that 
the  dielectric  strengths  of  the  feldspar  porcelains  are  from  one 
and  one-half  to  twice  those  of  the  lime  porcelains. 

CONCLUSIONS. 
Conclusions  which  may  be  drawn  from  the  foregoing  work 
indicate  that: 

1.  For  all  practical  purposes,  the  dielectric  strength  is 
proportional  to  the  thickness  of  the  porcelain,  which  is  in  con- 
firmation of  that  assumption. 

2.  Rapid  burning  or  slow  burning,  rapid  cooling  or  slow 
cooling  do  not  materially  affect  the  dielectric  strength  of  high 
tension  insulators  so  long  as  such  treatment  does  not  develop 
blebs,  cracks  or  other  flaws. 

3.  The  average  of  all  tests  made  in  this  work  showed  that 
the  molecular  substitution  of  soda  feldspar  for  potash  feldspar 
in  a  porcelain  decidedly  increased  the  dielectric  strength. 

4.  High-grade  fire  clays  are  capable  of  making  high  tension 
insulators  giving  as  high  a  dielectric  strength  as  the  average 
potash  feldspar  porcelain  vitrifying  at  the  same  temperature. 

5.  The  substitution  of  a  stoneware  clay  for  No.  1  plastic 
fire  clay  lowers  both  the  maturing  temperature  and  the  dielectric 
strength. 

6.  A  body  made  vitreous  by  the  use  of  lime  without  feldspar 
gives  a  porcelain  of  low  dielectric  strength. 

DISCUSSION. 
Mr.  Purdy:     I  note  that  he  has  a  series  in  which  calcium 
carbonate  is  varied  against  calcined  clay.     An  explanation  of  the 


36  DIELECTRIC    STRENGTH    OF    PORCELAINS. 

philosophy  of  a  substitution  of  such  unlike  materials  would  be 
of  interest. 

I  note  also  that  he  reports  that  a  piece  which  has  already 
been  punctured  will  show  a  lower  but  relatively  high  strength 
when  tested  the  second  time  at  the  same  point  and  the  same  high 
strength  when  the  same  test  piece  is  punctured  at  a  new  point. 
The  only  fact  of  value  in  these  observations  is  the  efficiency  of 
oil  as  a  non-conductor.  When  puncturing  under  oil  the  hole 
thus  caused  is  filled  with  oil  and  not  by  glass  as  Mr.  Radcliffe 
thinks.  You  can  not  re-test  a  punctured  piece  in  the  air  as  they 
did  in  the  oil.  In  fact  they  could  not  have  tested  those  shallow 
pieces  in  the  air  at  all  because  of  arcing  around.  Their  data, 
therefore,  on  these  two  points  is  of  value  only  for  insulation 
under  oil.  Their  conclusion  should  have  been  that  their  porcelain 
test  pieces  had  but  little,  if  any,  better  dielectric  strength  than 
did  the  oil  they  were  using. 

Prof.  Siull:  In  order  to  satisfy  Prof.  Purdy's  interest  re- 
garding the  replacement  of  calcined  clay  by  calcium  carbonate, 
I  will  say  that  the  calcined  clay  was  employed  merely  for  con- 
trolling the  working  properties  and  drying  shrinkages  of  the 
bodies,  as  was  mentioned  when  the  paper  was  read.  No  attempt 
whatever  was  made  to  get  a  comparison  of  the  bodies  by  variable 
lime-calcined  clay.  The  object  in  view  was  merely  to  obtain 
vitreous  bodies  by  using  lime  without  resorting  to  additions 
of  feldspar,  and  to  compare  the  dielectric  strengths  of  these 
lime  bodies  with  those  of  feldspar  bodies  previously  made. 

There  is  no  "hole"  left  after  the  porcelain  has  been  punctured. 
Several  of  these  crock  shaped  test  pieces,  after  puncturing, 
were  used  as  convenient  receptacles  for  calcining  small  samples 
of  kaolin  at  iooo°  C.  At  this  temperature  the  oil  was  com- 
pletely burned  off.  Some  of  these  trial  pieces  were  broken 
through  the  line  of  puncture  after  they  had  served  their  purpose 
in  calcining  clay  and  these  pieces  showed  plainly  that  the  "hole" 
was  filled  with  a  glass. 

Mr.  Radcliffe  shows  that  repeated  puncturing  through  the 
same  spot  gradually  weakens  the  dielectric  strength.  If  punctur- 
ing leaves  a  hole  and  this  hole  is  filled  with  oil,  then  why  would 


DIELECTRIC    STRENGTH    OF    PORCELAIN'S.  37 

not  repeated  puncturing  after  the  first  give  the  same  voltage 
readings  for  puncturing  the  column  of  oil  filling  the  hole? 

The  use  of  the  oil  bath  is  merely  to  prevent  arcing.  If 
the  trial  pieces  had  been  made  of  suitable  size  and  shape  to 
prevent  arcing  when  tested  in  air,  there  is  no  reason  why  they 
would  not  have  shown  the  same  dielectric  strengths  in  air  as  they 
did  in  oil. 

The  results  are  comparative  whether  the  porcelains  are 
tested  in  air  or  in  oil.  Either  set  of  conditions  would  show 
the  porcelains  of  highest  dielectric  strength. 

NOTES  PREPARED  AFTER  READING  THE  PAPER. 

Mr.  Minncman:  This  paper  by  Mr.  Radcliffe  is  a  valuable 
addition  to  our  ceramic  literature,  for  the  reason  that  so  little 
experimental  data  is  available  along  these  lines. 

I  think,  however,  that  certain  of  his  conclusions  are  drawn 
too  directly  from  his  actual  results,  neglecting  other  conditions 
which  are  bound  to  enter  in. 

In  regard  to  the  dielectric  strength  of  soda-feldspar  versus 
potash  feldspar,  Mr.  Radcliffe  says:  "The  soda  feldspar  bodies 
have  higher  dielectric  strengths  than  the  corresponding  potash 
feldspar  bodies"  and  "The  average  of  all  tests  made  in  this  work 
showed  that  the  molecular  substitution  of  soda  feldspar  for  potash 
feldspar  in  a  porcelain  decidedly  increases  the  dielectric  strength." 
However,  upon  looking  over  the  individual  test  results,  it  is  seen 
that  in  eleven  cases  the  corresponding  soda  feldspar  bodies  show 
higher  dielectric  strength  while  in  the  remaining  eight  cases 
the  corresponding  potash  feldspar  bodies  show  the  higher  dielec- 
tric strength.  Averaging  the  dielectric  strengths  of  all  the  soda 
feldspar  bodies  and  all  the  potash  feldspar  bodies,  we  find  the 
soda  feldspar  bodies  have  only  about  2.5  per  cent,  higher  dielec- 
tric strength  than  the  corresponding  potash  feldspar  bodies. 
This  appears  to  be  a  decided  increase  in  the  dielectric  strength, 
but  when  it  is  remembered  that,  in  the  method  used  in  testing, 
voltage  readings  accurate  to  several  per  cent,  are  almost  impossi- 
ble, and  variations  up  to  10  per  cent,  are  quite  possible,  this 
difference  of  2.5  per  cent,  seems  almost  negligible. 

The  voltage  readings  in  these  tests  were  taken,  I  under- 
stand, from  a  voltmeter  placed  across  the  low  tension  side  of  the 


38  DIELECTRIC    STRENGTH    OF    PORCELAINS. 

transformer,  getting  a  calibration  curve  between  the  volts  pri- 
mary and  volts  secondary  by  means  of  a  needle  gap  in  the  high 
tension  side.  The  readings  could,  therefore,  not  be  more  accurate 
than  readings  from  the  needle  gap  which  would  be  from  one 
to  four  per  cent.,  depending  upon  the  experience  of  the  observer. 
Add  to  this  numerous  uncontrollable  variables,  such  as  varying 
weather  conditions,  growth  of  charge  in  the  circuit,  variation 
in  wave  form  and  the  time  element  in  testing  and  it  is  evident 
that  a  wide  divergence  is  quite  possible. 

That  such  a  variation  occurs,  may  be  seen  from  the  results 
obtained  by  Messrs.  Bleininger  and  Stull,  Vol.  XII,  Trans.  A. 
C.  S.,  p.  638,  who  made  tests  on  the  same  porcelains  fired  at 
approximately  the  same  heat  treatment  and  tested  with  the 
same,  or  a  very  similar,  apparatus.  Comparing  their  results 
on  the  same  trials  and  with  Radcliffe's  results  we  find  variations 
up  to  25  per  cent. 

Considering  these  points,  I  should  say  that  Mr.  Radcliffe's 
results  tend  to  show  that  the  dielectric  strength  of  a  porcelain  is 
the  same  whether  made  from  soda  feldspar  or  potash  feldspar 
so  long  as  the  porcelain  is  well  vitrified  and  dense. 

In  regard  to  the  use  of  lime,  Mr.  Radcliffe  concludes  that 
"a  porcelain  made  vitreous  by  the  use  of  lime  without  feldspar 
gives  a  porcelain  of  low  dielectric  strength." 

It  must  be  remembered  that  Mr.  Radcliffe  replaced  his 
feldspar  with  lime  and  calcined  china  clay,  thereby  making  a 
body  of  an  entirely  different  structure.  It  is  evident  that  a  body 
made  up  with  calcined  clay  and  lime  in  place  of  feldspar  would 
behave  quite  differently,  due  to  the  lesser  distribution  of  the  lime 
particles  and  the  resulting  differences  in  fusion,  just  as  a  body 
made  up  with  equivalent  amounts  of  sodium  carbonate  and 
calcined  clay  would  differ  from  a  body  made  up  with  soda  feld- 
spar. Had  the  clay  and  lime  been  fritted  and  ground  until  a 
homogeneous  mixture  was  reached  before  being  used  in  the  porce- 
lain, I  think  that  entirely  different  results*  might  have  been  ob- 
tained. I  agree  with  Bleininger  and  Stull  that  dielectric  strength 
"depends  more  upon  sound  vitrification  and  good  mechanical 
structure  than  upon  chemical  composition." 


DIELECTRIC    STRENGTH    OF    PORCELAINS.  39 

Mr.  Radeliffe's  results  do,  however,  show  that  lime  used 
in  porcelain  in  this  way  materially  shortens  the  firing  range. 

The  great  volume  of  high  voltage  porcelain  is  not  used 
under  oil  but  in  air  and  tests  under  oil  often  give  entirely  different 
results  than  do  air  tests.  It  is  particularly  noticeable  that  a 
porcelain  not  completely  vitrified  and  having  considerable  ab- 
sorption shows  up  very  well  when  tested  under  oil,  but  breaks 
down  much  earlier  when  tested  in  air  with  the  bottom  of  the  test 
piece  placed  in  water  as  is  done  in  commercial  tests. 

.Mr.  Radcliffe  mentions  the  puncturing  of  a  piece  under  oil 
repeatedly  in  the  same  spot.  When  testing  porcelain  in  air, 
after  puncture  once  takes  place  there  is  a  continuous  flow  of  the 
current,  and  the  piece  ceases  to  act  as  an  insulator.  When 
testing  under  oil,  however,  this  repeated  puncture  at  a  lower 
voltage  often  takes  place,  which  leads  me  to  believe  that  the  oil 
protects  the  punctured  spot  sufficiently  to  give  considerable 
insulation  after  the  first  puncture. 

Consequently  I  should  say  that  tests  made  in  air,  more  nearly 
approximating  conditions  under  which  high  voltage  porcelain 
is  used  commercially,  would  be  of  much  more  practical  value. 

Prof.  St  nil:  The  question  of  experimental  errors  enters 
into  all  research  work  of  this  character.  In  theory,  however, 
there  is  such  a  thing  as  absolute  accuracy.  The  value  of  research 
work  depends  largely  upon  the  accuracy  in  executing  the  work 
and  the  extent  to  which  experimental  errors  are  avoided  or  elimi- 
nated. 

One  of  the  greatest  sources  of  error  which  Mr.  Minneman 
failed  to  mention  is  due  to  variations  in  structure  of  different 
pieces  made  from  the  same  body.  It  is  impossible  to  eliminate 
minute  air  bubbles  and  to  mould  two  pieces  of  porcelain  so  that 
they  will  have  identically  the  same  structure. 

Where  it  is  impossible  to  eliminate  experimental  errors 
or  to  deduct  such  errors  by  calculations  from  known  data,  it  is 
customary  to  make  several  tests  and  to  consider  the  mean  average 
as  a  means  of  reducing  such  errors  to  a  minimum. 

As  has  been  mentioned,  Mr.  Radcliffe  made  from  five  to  ten 
different  puncture  tests  for  each  different  body  under  each  differ- 
ent set  of  conditions,  excluding  all  trials  in  which  Haws  due  to 


4-0  DIELECTRIC    STRENGTH    OF    PORCELAINS. 

moulding  were  apparent  and  taking  the  mean  average  of  ap- 
parently sound  pieces. 

Mr.  Minneman  states  that  "it  is  seen  that  in  eleven  cases 
the  corresponding  soda  feldspar  bodies  show  higher  dielectric 
strength  while  in  the  remaining  eight  cases  the  corresponding 
potash  feldspar  bodies  show  higher  dielectric  strength." 

It  was  stated  in  Mr.  Radcliffe's  paper  when  read  that  "bodies 
C  and  Ci  are  rejected  on  account  of  their  porosities"  (in  the 
first  burn).  Since  these  two  bodies  are  porous  they  are  not  at 
all  comparable  with  the  others  which  were  well  vitrified,  hence, 
it  is  legitimate  and  proper  to  exclude  them  from  the  calculations. 
Excluding  C  and  Ci  in  the  first  burn,  it  is  observed  that  the  com- 
parison is  as  twelve  to  seven,  as  Mr.  Minneman  has  evidently 
made  an  error  in  count. 

Since  five  trials  of  each  porcelain  for  each  of  the  four  burns 
were  tested,  the  average  puncture  voltage  per  mm.  (excluding 
C  and  Ci  in  the  first  burn)  is  calculated  on  ninety-five  trials 
punctured  for  each  type  of  porcelain.  Taking  the  average 
of  such  a  large  number  of  tests  tends  to  give  an  accurate  com- 
parison. 

The  physical  properties  of  ceramic  mixtures  depend  upon 
composition  and  method  of  treatment.  The  treatment  of  the 
potash  feldspar  porcelains  and  the  corresponding  soda  feldspar 
ones  were  carried  out  as  nearly  alike  as  possible.  Since  the  two 
different  kinds  of  feldspars  are  bound  to  exert  some  differences 
upon  the  physical  properties,  and  one  of  these  physical  properties 
is  "dielectric  strength,"  it  is  more  logical  to  conclude  that  the 
substitution  of  soda  feldspar  for  potash  feldspar  has  increased 
the  dielectric  strength  since  this  conclusion  is  backed  by  the 
average  results  of  ninety-five  puncture  tests  of  each  of  the  two 
types  of  porcelain. 

Mr.  T.  H.  Armine:  The  puncture  tests  made  upon  the 
porcelains  referred  to  in  Mr.  Radcliffe's  paper  were  made  under 
my  supervision  in  the  Engineering  Experiment  Station  at  the 
University  of  Illinois. 

The   accompanying  sketch   shows   the   connections  used   in 


DIELECTRIC    STRENGTH    OF    PORCELAINS. 


41 


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the  test:  G  is  a  generator  of  60  kilowatts  capacity  which  pro- 
duces practically  a  sine  wave  of  electromotive  force.  T  is  a 
transformer  stepping  the  voltage  of  the  generator  up  by  a  four 
to  one  ratio.  HT  is  a  transformer  of  10  kilowatts  capacity  which 
is  designed  to  step  from  440  up  to  100,000  volts.  FR  is  the 
field  rheostat  of  the  generator  by  means  of  which  the  high  tension 
voltage  was  varied.  O  is  a  stoneware  jar  having  a  brass  electrode, 
E,  inserted  through  a  hole  in  its  bottom.  A  similar  electrode, 
E1,  was  arranged  in  such  a  manner  that  it  was  brought  in  the 
same  straight  line  as  E  and  so  that  it  could  be  pulled  up  away 
from  E  to  permit  of  putting  the  porcelain  sample  TS  between  the 
electrodes. 

The  first  procedure  was  to  obtain  a  calibration  curve  of 
the  apparatus.  The  connection  was  removed  from  the  electrode 
E  and  E1  and  a  needle  gap  was  placed  across  the  high  tension 
side  of  the  transformer.  With  various  settings  of  the  needle 
gap  the  voltage  was  gradually  brought  up  by  varying  FR  until 
the  discharge  took  place  across  the  gap,  at  which  time  the  voltage 
on  the  low  tension  side  of  the  transformer  was  read  by  means 
of  the  voltmeter  Ym.  In  this  way  the  relation  between  "volts 
primary"  and  "length  of  the  needle  gap"  was  obtained.  Then 
by  means  of  the  well  known  A.  I.  E.  E.  curve  between  "distance 
between  needle  points  in  air"  and  "volts,"  the  "centimeters 
width  of  needle  gap"  were  translated  into  "volts  secondary." 
This  calibration  was  repeated  several  times  and  good  checks 
were  obtained  so  the  average  curve  between  "volts  primary" 
and  "volts  secondary"  was  adopted  as  the  calibration  curve. 


42  DIELECTRIC    STRENGTH    OF    PORCELAINS. 

In  making  the  puncture  tests  the  connection  was  made  as 
shown  in  the  diagram,  a  porcelain  test  piece,  TS,  was  placed  be- 
tween the  electrodes  and  the  stoneware  jar  O  filled  with  trans- 
former oil.  The  voltage  was  gradually  brought  up  by  varying 
FR  until  puncture  took  place,  at  which  time  the  "volts  primary" 
were  read  by  means  of  the  voltmeter  Ym.  By  means  of  the  cali- 
bration the  curve  "volt  secondary,"  that  is,  the  volts  to  produce 
rupture,  could  be  obtained.  In  all  the  tests  care  was  taken  that 
the  rate  of  increase  in  voltage  was  uniform  for  all  samples. 

In  Mr.  Minneman's  discussion  of  this  paper  the  question  of 
accuracy  of  the  results  obtained  is  brought  up.  Since  the  cali- 
bration curve  was  obtained  by  reference  to  a  needle  gap  it  may 
be  in  error  by  as  much  as  4  per  cent.  Since  it  was  made  all  in 
one  day  under  as  constant  conditions  of  weather,  etc.,  as  possible 
and  since  several  checks  were  made  it  is  probable  that  the  error 
in  calibration  is  less  than  this.  However  great  the  error  in  the 
calibration  curve  is,  it  is  a  constant  error  and  affects  the  reading 
only  when  considered  as  absolute  values  of  voltage  and  does  not 
affect  the  relative  values  obtained  for  the  various  samples.  For 
instance,  the  tests  upon  soda  feldspar  vs.  potash  feldspar  involve 
none  of  "the  uncontrollable  variables  such  as  varying  weather 
conditions,  growth  of  charge,  variation  of  wave  form  and  time 
element,"  mentioned  by  Mr.  Minneman.  The  values  obtained 
for  these  two  porcelains  should  be  closely  comparable  even  if 
the  absolute  values  of  voltage  were  seriously  in  error  since  the 
errors  should  be  the  same  for  both  sets  of  tests. 

Mr.  Minneman  also  mentions  that  "when  testing  a  porcelain 
in  air,  after  puncture  takes  place  there  is  a  continuous  flow  of 
current  and  the  piece  ceases  to  act  as  an  insulator."  This  same 
action  takes  place  with  tests  under  oil.  At  the  instant  of  rupture 
the  current  follows  the  arc  and  continues  to  follow  it  as  long  as 
the  voltage  is  on  in  the  same  way  as  it  does  with  a  test  in  air. 
A  second  application  of  voltage  in  the  same  spot  does  show 
that  there  is  still  considerable  dielectric  strength  after  the  first 
puncture.  This  dielectric  strength  is  not,  however,  due  to  the 
protective  effect  of  the  oil.  The  current  which  follows  the  arc 
fuses  the  porcelain  and  when  the  circuit  is  broken  the  fused  porce- 


DIELECTRIC   STRENGTH   OF   PORCELAINS.  4,} 

lain  solidifies  in  place,  forming  a  glassy  spot.  Due,  perhaps, 
to  flaws  and  to  the  presence  of  foreign  material  such  as  carbonized 
oil,  which  probably  prevents  the  formation  of  a  homogeneous 
structure,  the  strength  on  second  puncture  is  less  than  on  the 
first.  The  voltage  at  which  a  sample  will  puncture  the  second 
time  has,  I  believe,  no  relation  to  the  real  dielectric  strength, 
i.  i,  on  first  puncture,  of  the  porcelain  sample.  I  believe  that 
the  only  serious  effect  of  testing  under  oil  would  be  with  very 
poorly  vitrified  porcelains  such  as  are  obviously  not  fit  for  high 
tension  insulators.  In  testing  these  porous  porcelains  comparable 
results  possibly  would  not  be  obtained  under  oil. 


UNIVERSITY  OF  ILLINOIS  BULLETIN 


Vol.  X.  SEPTEMBER   16,  1912.  No.  3 


[Entered  February  14,  1902,  at  Urbana,  Illinois,  as  second-class  matter  under 
Act  of  Congress  of  July  16,  1894.] 


BULLETIN  No.  17 
DEPARTMENT  OF  CERAMICS 

A.  V.  BLE1NINGER,  Director 


THE  EFFECT    OF  ACID5    AND  ALKALIES  UPON 
CLAY  IN  THE  PLASTIC  STATE 

BY 
A.  V.  BLLININGLR  AND  C.  E.  FULTON 

NOTE  ON  THE  DISSOCIATION  OF  CALCIUM 
HYDRATE 

BY 
R.  K.  HURSH 


NOTE  ON  THE  RELATION  BETWEEN  PREHEAT- 
ING TEMPERATURE  AND  VOLUME 
SHRINKAGE 


BY 
R.  K.  HURSH 

1911-1912 


PUBLISHED  FORTNIGHTLY  BY  THL   UNIVERSITY 


[Reprinted  from  Transactions  American  Ceramic  Society,     Vol.  XIV, 
by  Permission.] 

THE  EFFECT  OF  ACIDS  AND  ALKALIES  UPON  CLAY  IN  THE 
PLASTIC  STATE. 
A.  V.  Bleininger  and  C.  E.  Fulton,  Urbana,  111. 

INTRODUCTION. 

The  effect  of  acids,  alkalies  and  salts  upon  clay  suspensions 
(slips)  has  been  discussed  frequently,  and  the  work  of  Simonis, 
Mellor,  Rieke,  Boettcher,  Ashley,  Foerster  and  Bollenbach  deals 
with  the  viscosity  and  other  phenomena  of  systems  in  this  state. 
But  little  is  known  concerning  the  effect  of  such  reagents  upon 
clays  in  the  plastic  condition  which  differs  from  that  of  a  sus- 
pension, due  to  the  cohesive  influence  of  the  particles  upon  each 
other. 

It  has  been  realized  for  some  time  that  the  properties  of  clays 
in  the  wet  state  are  influenced  by  the  presence  of  alkalies  and 
acids.  Seger  explains  the  increase  in  the  plasticity  of  clay  upon 
storing  by  the  assumption  that  the  fermentation  of  organic  sub- 
stances results  in  acids  which  neutralize  the  alkalinity  due  to  the 
decomposed  feldspar,  and  in  addition  bring  about  the  "sour" 
condition  which  accompanies  the  improvement  in  working 
qualities.  Rohland1  discusses  this  subject  from  the  theoretical 
standpoint  and  makes  quite  definite  statements  with  reference 
to  the  principles  underlying  the  effect  of  various  reagents  upon 
clays  in  the  plastic  state.  He  arrives  at  the  conclusion  that  the 
plasticity  of  clays  is  increased  by  the  presence  of  H+  ions,  while, 
on  the  other  hand,  the  OH'  ions  are  active  in  the  opposite  direc- 
tion. According  to  Rohland,  the  plasticity  is  likewise  increased 
by  the  addition  of  colloids  like  tannin,  dextrine,  etc.,  as  has  been 
shown  by  the  work  of  Acheson,  fine  grinding  and  the  storage  of 
the  clay  in  cool  and  moist  places.  It  is  supposed  that  the  in- 
crease in  plasticity  is  coincident  with  the  coagulation  which  is 
primarily  due  to  the  presence  of  the  hydrogen  ions;  it  is  retarded 
by  the  hydroxyl  ions.  The  salts  of  strong  bases  and  weak  acids 
which  dissociate  OH'  ions  hydrolytically  produce  an  effect 
similar  to  that  of  the  hydroxyl  ions.  Neutral  salts,  Rohland 
goes  on  to  say,  with  but  few  exceptions,  are  indifferent  in  their 


1  "Die  Tone,"  pp.  35-19. 


4  EFFECT    OF   ACIDS   AND   ALKALIES    UPON    CLAY. 

effect,  though  some  appear  to  show  a  contradictory  behavior, 
which  has  not  yet  been  explained.  "The  effect  of  the  hydroxyl 
ions  may  be  weakened,  compensated  or  strengthened  by  the  action 
of  the  salt  in  question.  Thus  borax  is  an  example  of  the  first 
class  and  sodium  carbonate  of  the  second." 

The  same  writer  further  says  that  with  some  clays  the  addi- 
tion of  Na2C03  brings  about  an  improvement  in  plasticity,  while 
ordinarily  the  same  reagent  behaves  in  the  opposite  sense,  due 
to  the  hydrolytic  dissociation  of  OH'  ions.  It  is  possible  that 
the  effect  of  hydroxyl  ions  might  be  neutralized  by  the  C03" 
ions. 

DRYING  SHRINKAGE. 

A  decided  lack  of  data  exists  with  reference  to  the  deter- 
mination of  the  effect  of  reagents  upon  the  plasticity  of  clays. 
It  was  thought  advisable  for  this  reason  to  begin  work  along 
this  line  without  reference  to  any  theoretical  speculations.  The 
most  obvious  criterion  to  be  used  in  this  connection  is  the  drying 
shrinkage,  which,  from  what  we  know  of  the  properties  of  clays, 
is  a  function  of  plasticity.  It  is  evident  that  any  effect  caused 
by  the  addition  of  reagents  will  at  once  be  indicated  by  the 
shrinkage  of  the  clay. 

In  this  series  of  experiments  Georgia  kaolin  was  used.  This 
clay  was  found  to  show  an  acid  reaction  when  tested  with  phenol- 
phthalein.  This  would  indicate  that  the  addition  of  acid  should 
bring  about  no  decided  change  in  the  clay,  a  fact  which  was 
verified  by  experiment.  The  reagents  employed  were  HC1, 
H2S04,  NaOH  and  Na2C03.  In  carrying  out  the  work  a 
thoroughly  mixed  sample  was  first  prepared  so  that  variations 
due  to  differences  in  composition  were  reduced  to  a  minimum. 
The  test  specimens  were  in  the  shape  of  bars  35/16x  i  x  5/8  inches. 
Even  the  most  careful  linear  shrinkage  measurements  by  means 
of  the  vernier  caliper  were  found  to  be  unsuitable  for  the  work. 
A  volumenometer  permitting  of  readings  to  0.05  cc.  was  then 
employed.  The  measuring  liquid  used  was  petroleum  from  which 
the  lighter  oils  had  been  expelled  by  heating.  The  bars  were  at 
once  weighed  and  allowed  to  dry  at  the  laboratory  temperature 
for  three  days,  after  which  they  were  heated  at  no°  to  constant 


EFFECT    OF    ACIDS    AND    ALKALIES    UPON    CLAY.  5 

weight,  and  their  shrinkage  determined.  For  each  concentration 
of  reagent  three  bars  were  made  and  measured. 

Clay  and  Water. — A  study  was  first  made  of  the  drying 
shrinkage  of  the  clay  with  different  amounts  of  water,  ranging 
from  the  soft  state  in  which  the  clay  could  be  barely  molded 
to  the  condition  of  minimum  water  content  when  molding  was 
likewise  difficult  for  the  opposite  reason.  The  shrinkage  rela- 
tions to  the  various  contents  of  water  are  shown  in  Fig.  i.  The 
third  point  on  the  curve,  showing  a  shrinkage  of  10.45  Per  cent, 
with  a  water  content  of  32.8  per  cent.,  represents  the  most  work- 
able state.  Any  increase  in  water  above  this  point  is  at  once  ob- 
served by  the  rapid  softening  of  the  mass.  The  clay  hence  is  well 
suited  for  the  work  at  hand,  owing  to  the  ease  with  which  the 
condition  of  best  working  behavior  is  recognized  in  distinction 
from  many  other  plastic  clays  which  possess  a  long  working 
range. 

Effect  of  Acid. — Upon  adding  from  0.025  to  0.525  gram  of  hy- 
drochloric acid  to  100  grams  of  clay,  we  observe  from  Fig.  2  that  the 
shrinkage  is  not  materially  affected  by  this  reagent.  While  two 
maxima  of  somewhat  greater  contraction  are  noted,  the  principal 
result  seems  to  be  a  reduction  in  shrinkage,  contrary  to  what 
might  be  expected  from  Rohland's  statements.  The  fact  re- 
mains, however,  that  conditions  are  more  complex  than  they 
seem,  due  to  the  probable  solution  of  various  salts  in  the  clay 
as  well  as  the  formation  of  some  chlorides  by  the  acid. 

It  was  thought  that  further  insight  into  the  effect  of  the  acid 
might  be  obtained  by  calculating  the  total  and  the  shrinkage 
water  in  terms  of  the  true  clay  volume,  i.  c,  weight  divided  by 
the  density  of  the  powdered  substance,  according  to  the  rela- 
tion : 

100  Qt  —  v2) 

w  —  per  cent,  (by  volume)  shrinkage  water. 

~d 
Where  vt  =  volume  of  wet  brickette, 
v2  =  volume  of  dry  brickette, 
w  =  weight  of  brickette,  dried  at  no°  C, 
d  =  density  of  the  dry  and  powdered  clay. 


EFFECT  OF  ACIDS  AND  ALKALIES  UPON  CLAY. 


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IO       EFFECT  OF  ACIDS  AND  ALKALIES  UPON  CLAY. 

Similarly,  the  volume  of  the  total  water  in  terms  of  the  true 
clay  volume  is  calculated. 

In  the  diagram  of  Fig.  3,  the  respective  volumes  of  total  and 
shrinkage  water  are  shown.  The  boundary  between  the  volumes 
of  water  and  that  of  clay  is,  of  course,  the  line  representing  zero 
water  and  100  volume  per  cent,  of  clay.  It  is  shown  in  Fig.  3 
that  the  content  of  pore  water  has  been  decreased,  that  of  the 
shrinkage  water  having  been  increased  both  at  the  expense  of  the 
pore  water  and  due  to  the  rise  in  the  total  water  content  at  the 
two  max.  points. 

The  addition  of  sulphuric  acid  likewise  tends  to  decrease  the 
shrinkage  as  is  shown  in  the  diagram  of  Fig.  4. 

Effect  of  Alkalies. — The  influence  of  NaOH  is  illustrated 
in  the  diagram  of  Fig.  5.  It  is  at  once  noted  that  with  0.2  per 
cent,  of  this  reagent  a  striking  max.  point  is  reached,  indicating 
a  marked  increase  in  shrinkage,  contrary  to  what  we  should  ex- 
pect according  to  Rohland's  views.  Only  after  adding  larger 
amounts  does  the  contraction  descend  towards  the  normal  value. 
Here  again,  according  to  Fig.  6,  the  increased  shrinkage  is  due  in 
part  to  the  specific  effect  of  the  reagent  in  increasing  the  distance 
between  the  particles  in  the  plastic  state  and,  in  part,  to  the 
denser  structure  of  the  clay  upon  drying.  Beyond  the  max. 
point  this  condition  changes,  since  the  pore  water  line  rises  above 
the  normal  level.  Since,  at  the  same  time,  the  total  water  line 
descends,  the  shrinkage  is  gradually  decreased.  The  structure 
of  the  dried  clay  is  thus  more  open  with  the  higher  contents  of 
NaOH  than  with  the  smaller  additions. 

The  growth  in  shrinkage  is  still  more  pronounced  in  the  case 
of  Na2C03,  Fig.  7,  a  phenomenon  contrary  again  to  Rohland's 
statements,  although,  of  course,  in  this  case  the  effect  of  the 
C03  ion  might  have  proven  a  factor,  especially  if  absorption  has 
taken  place  to  any  appreciable  extent.  However,  even  under 
this  assumption,  it  is  somewhat  improbable  that  the  carbonic 
acid  could  have  brought  about  such  a  change  where  other  acids 
failed  to  accomplish  anything  like  the  same  result.  In  this 
diagram  the  maximum  occurs  with  0.7  per  cent,  of  the  reagent. 
With  larger  concentrations  the  shrinkage  is  again  reduced,  but 
appears  to  gain  once  more  with  amounts  beyond   1.2  per  cent. 


EFFECT    OF    ACIDS   AND   ALKALIES    UPON    CLAY.  I  I 

As  may  be  observed  from  the  diagram  of  Fig.  8,  the  pore  water 
volume  is  diminished  throughout  this  series  with  a  gradually 
increasing  total  water  content  up  to  the  maximum. 

DE7L0CCULATI0N  SERIES. 
It  was  thought  desirable  to  study  the  effect  of  the  acids  and 
alkalies  upon  the  clays  as  regards  dellocculation,  using  solutions 
of  the  same  concentration  present  in  the  plastic  clay,  as  shown 
by  the  preceding  curves.  To  illustrate:  If  to  ioo  grains  of  clay, 
requiring  34.9  per  cent,  of  water,  0.025  gram  Na2C03  was  added, 
this  would  represent  a  solution  carrying  0.025  -4-  34.9  =  0.000716 
gram   Na2C03  per  cubic  centimeter  of  water.      Such    solutions 


Fig.  9. 


No. 

Wt.  clay. 
Grams 

Wt.  Na2C03, 
Grams 

Water, 
cc. 

Volume  of 

sediment, 

cc. 

Condition  of 

turbidity  of 

supernatant  liquid 

O 

5 

98 

18.O 

Clear 

I 

5 

O.0713 

98 

19-5 

" 

2 

5 

O.1423 

98 

21.8 

tt 

3 

5 

O.2296 

98 

24-3 

" 

4 

5 

0.4529 

98 

28.O 

" 

5 

5 

O . 6803 

98 

27-4 

it 

6 

5 

0.891  j 

98 

28.0 

a 

7 

5 

1.0659 

98 

28.0 

tt 

8 

5 

1-3549 

98 

28.0 

a 

9 

5 

i-55" 

98 

28.0 

it 

12 


EFFECT    OF    ACIDS   AND   ALKALIES   UPON    CLAY. 


were  made  up  of  concentrations  corresponding  to  the  various 
points  in  the  preceding  curves.  In  each  case  to  5  grams  of  clay 
98  cc.  of  the  solution  were  added  in  a  graduated  tube.  The 
tubes  were  placed  in  a  shaking  machine  for  90  minutes  and 
allowed  to  stand.  It  was  found  that  the  clay  itself,  without  any 
reagent,  settled  well,  showing  a  clear,  supernatant  liquid  and  a 
sediment  occupying  18  cc. 

It  was  shown  that  the  addition  of  acid  produced  no  change, 
excepting  in  the  volume  of  the  sediment,  which  was  finally  in- 
creased from  18  to  28  cc,  as  is  observed  from  Fig.  9. 

The  sodium  carbonate  solutions,  on  the  other  hand,  started 
with  conditions  of  complete  deflocculation  (Fig.  10).  The  sediment 
volumes  are  shown  in  the  table  accompanying  each  figure. 


Fig.  10. 


No. 

wt. 

clay, 

grains 

Wt.  Na2C03, 
grams 

Water, 
cc. 

Volume  of 

sediment, 

cc. 

Condition  of  turbidity  of 
supernatant  liquid 

O 

I 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

5 

5 
5 
5 

5 
5 
5 
5 
5 
5 
5 
5 

O.0702 
O. 1426 
O . 2090 
O. 2822 

0-57I3 
O.8388 
I . 3642 
I-857I 
2.5059 
3 ■ 4006 
4.0709 

98 
98 
98 
98 
98 
98 
98 
98 
98 
98 
98 
98 

18 

4-5 
19 
24 
24 
20 
20 
21 

19 
18 
18 
18 

Clear 

Very  turbid 

Very  turbid 

Slightly  less  turbid 

Less  turbid 

Slightly  turbid 

Slightly  turbid 

Almost  clear 

Clear 

Clear 

Clear 

Clear 

EFFECT    OF   ACIDS   AND   ALKALIES    UPON'    CI. AY.  13 

The  maximum  point  of  the  shrinkage  curve  corresponds  to 
tube  No.  S,  where  the  supernatant  liquid  is  clear  for  the  first 
time. 

CONCLUSIONS. 

The  writers  do  not  attempt  at  this  time  to  explain  the 
phenomena  on  theoretical  grounds.  It  is  evident  that  the  con- 
ditions are  quite  complex  and  in  order  to  explain  them  still  further 
modes  of  attack  must  be  sought  for.  The  rules  laid  down  by 
Rohland  do  not  seem  to  apply,  since  in  the  main  the  acids  cleat ly 
caused  shrinkage  to  decrease  while  the  alkalies  produced  the 
reverse  effect,  which  is  contrary  to  his  statements.  In  order  to 
be  fair,  however,  attention  must  be  called  to  the  fact  that  shrinkage 
in  this  work  has  been  considered  a  measure  of  plasticity,  while 
Rohland  speaks  of  plasticity  itself  without  attempting  to  correlate 
this  property  with  any  numerical  value.  As  is  well  known,  there 
is  at  the  present  time  no  clear  conception  as  to  the  relation  be- 
tween plasticity  and  shrinkage  excepting  the  general  fact  that 
the  plastic  clays  as  a  class  show  a  greater  drying  shrinkage  than 
the  leaner  ones. 

DISCUSSION. 

Mr.  R.  J.  Montgomery:  I  should  like  to  ask  Prof.  Bleininger 
how  long  those  slips  in  the  cylinders  had  stood  when  the  photo- 
graphs were  taken. 

Prof.  Bleininger:  Twenty-four  hours.  I  might  add  also 
that  in  making  the  volume  determinations  they  were  stored 
twelve  hours  in  a  moist  chamber  in  order  to  bring  about  some  sort 
of  an  equilibrium  between  the  clay  and  the  reagent. 

Mr.  Kerr:  I  should  like  to  raise  the  question  as  to  what 
determinations,  if  any,  were  made  of  the  electrolytes  present 
in  the  clay  before  the  acids  and  alkalies  were  added.  Was  any 
general  data  obtained  upon  this  point? 

Prof.  Bleininger:  No  direct  determination  was,  of  course, 
made.  However,  you  have  seen  the  series  of  tubes  which  ought 
to  indicate  pretty  clearly  to  one  familiar  with  this  work  whether 
the  initial  conditions  are  acid  or  alkaline.  We  are  principally 
endeavoring  to  get  at  the  experimental  facts  without  much  re- 
gard to  theoretical  assumptions.  The  evidence  so  far  obtained 
along  these  lines  is  not  sufficient  to  base  upon  it  any  definite 


0.  Gfi-  ;ll  Jb, 


14  EFFECT    OF    ACIDS    AND   ALKALIES    UPON    CLAY. 

line  of  procedure.  The  work  of  Yeimarn  especially  has  dis- 
turbed pievious  conclusions  by  his  very  startling  claims  with 
reference  to  colloids.  We  thought  it  wise  to  work  along  the  lines 
which  I  have  indicated. 

Mr.  Kerr:  The  only  point  which  I  wished  to  bring  up  was 
that  if  one  clay  contained  positive  ions  in  excess  and  another  clay 
negative,  the  addition  of  either  acid  or  alkali  to  one  clay  would 
not  correspond  to  a  similar  addition  to  the  other  clay.  Some 
clays  give  a  strongly  acid  reaction,  others  a  weakly  acid,  while 
still  others  are  somewhat  alkaline.  Data  upon  neutralization 
might  be  included. 

Prof.  Bleininger :  This  is  brought  out  in  the  deflocculation 
experiments.  At  the  same  time  corrections  work  very  well  in 
theory,  but  when  you  come  to  make  them  you  will  find  that 
neutralization  does  not  necessarily  follow.  I,  of  course,  want  to 
check  Mr.  Ashley's  work  in  this  investigation  in  a  general  way. 
I  realize  we  have  learned  a  good  deal  from  his  work  and  I  want 
to  say  that  he  is  to  be  given  great  credit  for  having  started  work 
of  this  kind. 

Mr.  Purdy:  I  would  like  to  ask  if  any  experiment  has  been 
made  to  determine  whether,  as  a  rule,  trivalent  electrolytes  coagu- 
late clays  more  readily  than  do  the  uni-  and  divaleat  salts. 

Prof.  Bleininger:  I  would  say  that  it  has  been  done  with 
various  materials. 

Mr.  Pnrdy:  Has  it  been  done  with  clays?  I  would  like  to 
see  some  experiments  tried  on  that  and  reported,  because  I  have 
been  unable  to  show  that  the  trivalent  salts  have  any  more  effect 
than  the  other.  That  is  one  of  the  respects  in  which  the  clay  is 
different. 

Prof.  Bleininger:     Mr.  Ashley,  of  course,  has  done  such  work. 

Mr.  Pnrdy:  That  is  what  he  did  not  do,  he  accused  himself 
on  that  point. 

Prof.  Bleininger:  I  think  he  did  work  with  phosphates.  Of 
course,  as  I  said  before,  this  work  is  being  continued  and  we 
expect  to  take  representative  reagents. 

Mr.  Kerr:  What  measurements  other  than  volume  shrinkage 
were  made? 

Prof.   Bleininger:     We  hope  to  take  up  various  things  in 


EFFECT  OF  ACIDS  AND  ALKALIES  UPON  CLAY.        1 5 

time.  One  of  them  is  a  vapor  tension  investigation,  for  which 
a  special  apparatus  is  now  being  designed. 

Prof.  Grout:  I  would  like  to  ask  if  the  curves  which  are 
drawn  there,  such  as  the  first  curve  which  you  show  on  the  screen, 
were  the  average  of  a  series  of  results  on  one  clay  or  just  one 
series  of  tests. 

Prof.  Bleininger:  Taken  as  the  average  of  three  determina- 
tions in  each  case. 

Prof.  Grout:  I  wondered  if  that  approximation  of  a  maxi- 
mum was  so  characteristic  that  you  could  report  it  for  publica- 
tion on  one  seiies  of  tests;  whether  your  area  of  determination 
was  not  such  that  you  might  not  safely  report  it. 

Prof.  Bleininger:  Well,  we  were  able  to  get  very  good 
checks,  also  we  notice  that  the  two  acids  are  behaving  very 
similarly.  We  recognize,  however,  that  there  are  a  good  many 
factors  involved  which  it  is  almost  impossible  to  correlate  in  a 
technical  investigation  of  this  kind.  Of  course,  if  we  were  to 
carry  on  this  investigation  from  a  strictly  physical  chemical 
standpoint,  we  would  proceed  along  somewhat  different  lines. 

Mr.  Potts:  I  would  like  to  ask  Prof.  Bleininger  just  what 
practical  application  he  expects  to  make  of  that  treatment. 
Does  he  propose  to  make  kaolins  plastic? 

Prof.  Bleininger:  I  haven't  any  idea  as  to  what  this  in- 
formation could  be  used  for  and  am  indifferent  in  regard  to  that 
point. 


[Reprinted  from  Transactions  American  Ceramic  Society,     Vol.  XIV, 
by  Permission.] 


NOTE  ON  THE  DISSOCIATION  OF  CALCIUM  HYDRATE. 

By  R.   K.   Hirsh. 

INTRODUCTION. 

The  present  study,  which  was  intended  to  be  of  a  techno- 
logical rather  than  of  physical-chemical  nature,  was  undertaken 
with  the  purpose  of  learning  more  regarding  the  properties  and 
behavior  of  the  compound  Ca(OH)2.  The  work  has  a  practical 
bearing  in  demonstrating  the  value  of  methods  of  thermal  study 
upon  problems  dealing  with  the  dehydration  of  limes,  cements 
and  plasters. 

A  number  of  values  have  been  given  for  the  dissociation 
temperature  of  calcium  hydrate.  Herzfeld1  says  that  dissocia- 
tion evidently  begins  at  470  °  to  500  °  C.  He  gives  the  thermal 
effect  of  slaking  CaO  as  1 .51  cals.  per  gram  of  Ca(OH),  and  the 
maximum  temperature  of  formation  as  468  °.  H.  Rose2  found 
that  pure  calcium  hydrate  lost  nothing  at  100°  C,  absorbed  CO, 
at  200  °  and  300  °,  and  began  to  lose  H20  at  about  400  °  C. 

Le  Chatelier3  gives  a  vapor  tension  of  100  mm.  at  3500  C, 
and  760  mm.  at  4500  C. 

Tichborne4  found  the  precipitate  from  a  heated  solution  of 
lime  water  to  show  a  loss  on  blasting  that  corresponded  to  the 
formula  3Ca0.2H20.  Others  using  similar  methods  failed  to 
find  such  a  hydrate. 

Dr.  Johnston,5  whose  work  is  taken  up  further  on,  found 
the  dissociation  pressure  of  Ca(OH)2  to  reach  760  mm.  at  547  °  C. 

METHODS  AVAILABLE. 

There  are  several  methods  of  studying  the  dissociation  of 
hvdrates,  such  as  the  making  use  of  heating  curves,  the  deter- 
mination of  the  aqueous  pressure  in  direct  or  differential  tensim- 
eters,  and  the  method  depending  upon  the  determination  of 
the  loss  of  weight  at  different  temperatures 


1  Handbuch  der  anorg.  Chem.,  C.  Damim-r. 

2  Pogg.  Ann.  du  Physik  u.  Chem.,  LXXXYI.  105. 

3  Handbuch  der  anorg.  Chem.,  22,  Gmelin-Kraut. 

4  Chemical  News,  XXIV,  199. 

5  Ztschr.    phys.  Chem.,  LXII,  330. 


1 8  NOTE)    ON    DISSOCIATION    OF    CALCIUM   HYDRATE. 

HEATING  CURVE  METHOD. 

A  portion  of  the  substance  is  placed  in  a  furnace  with  a 
thermocouple  touching  it  and  another  near  it.  The  furnace  is 
heated,  and  the  temperatures  of  the  furnace  and  substance  are 
noted.  At  the  point  where  dissociation  takes  place,  a  lag  may  be 
noted  in  the  heating  curve  due  to  the  endothermic  reaction,  i.  e., 
the  absorption  of  heat  due  to  the  expulsion  of  water.  It  is  fre- 
quently difficult  and  sometimes  impossible  to  determine  the  point 
by  this  means,  owing  to  the  small  amount  of  heat  required  for 
the  reaction  of  the  slow  rate  of  dissociation.  Distinction  may 
be  made  between  mechanically  held  or  dissolved  water  and  chem- 
ically combined  water.  In  the  case  of  chemical  water,  the  lag 
will  occur  abruptly  at  the  temperature  of  dissociation.  Mechan- 
ical or  dissolved  water  will  pass  off  gradually  over  a  range  of  tem- 
perature, and  the  lag  due  to  these  is  gradual,  showing  no  abrupt 
break  at  a  definite  temperature. 

In  the  use  of  heating  curves,  close  regulation  of  the  tempera- 
ture is  very  necessary  to  get  reliable  results.  There  should  be 
no  fluctuations  in  the  heating  of  the  furnace.  Three  general 
methods  may  be  followed  in  the  heating: 

Indiscriminate,  in  which  no  attention  is  given  to  the  rate  of 
the  furnace  curve,  and  only  the  lags  in  the  heating  curve  of  the 
substance  are  given  attention. 

Constant  rate,  in  which  the  temperature  of  the  furnace  is- 
raised  at  a  uniform  rate. 

Constant  difference,  in  which  a  uniform  difference  between 
furnace  temperature  and  that  of  the  material  is  maintained. 
This  method  is  the  best,  although  the  most  difficult  one  of  the 
three.  The  constant  rate  method  gives  good  points,  but  the  lag 
will,  in  most  cases,  be  sloped  instead  of  horizontal. 

AQUEOUS  PRESSURES  METHOD. 

Van  Bemmelen,  in  studying  the  dehydration  of  the  silicic 
acid  gel,  placed  his  samples  in  desiccators  containing  various 
concentrations  of  H2S04.  Constant  temperature  was  maintained, 
and  the  samples  were  kept  in  the  desiccators  for  sufficient  time 
to  reach  equilibrium  under  the  various  vapor  tensions.  By 
plotting  the  loss  of  weight  curve  for  the  several  concentrations 
of  H2S04  or  the  corresponding  vapor  pressures,  he  was  able  to- 


NOTE    OX    DISSOCIATION    OF    CALCIUM    HYDRATE. 


19 


determine  the  inversion  points  and  the  degrees  of  hydration  in 
each  case.  The  same  method  has  been  applied  by  Prof.  A.  V. 
Bleininger6  in  studying  the  moisture  in  clays. 

Dr.  John  Johnston7  studied  the  dissociation  pressures  of 
several  metal  hydroxides  and  carbonates,  using  two  experimental 
methods.  The  first  was  applied  for  hydroxides  alone  and  is  sim- 
ilar to  one  used  by  Brill.  A  small  crucible  containing  a  weighed 
portion  (about  1 . 5  mg.)  of  the  substance  was  suspended  in  a  small 
electric  furnace  through  which  a  current  of  air  free  from  C02  and 
of  definite  vapor  pressure  was  passed.  The  air  was  freed  from 
CO,  by  passing  through  NaOH,  then  saturated  with  moisture  by 
bubbling  through  a  Liebig  potash  bulb,  containing  water,   and 


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7  Ztschr.  phys.  Chem.,  LXII,  p.  330. 


20  NOTE    ON    DISSOCIATION    OF    CALCIUM    HYDRATE. 

was  heated  before  passing  to  the  furnace  to  prevent  any  conden- 
sation. The  temperature  of  the  water  in  the  Liebig  bulb  was 
regulated  by  immersing  it  in  a  water  bath.  The  furnace  was 
held  at  constant  temperature,  and  the  vapor  tension  maintained 
at  a  definite  value  for  10  minutes  by  regulation  of  the  water 
bath  temperature.  The  crucible  was  then  removed  from  the 
furnace  and  weighed  on  a  very  fine  balance.  Conditions  of  tem- 
perature and  vapor  pressure  were  so  regulated  that  the  substance 
maintained  constant  weight  or  gained  slightly  during  the  period, 
and  these  values  were  taken  as  the  corresponding  temperature 
and  dissociation  pressure  of  the  material.  The  results  of  this 
method  for  Ca(OH)2  are  shown  in  Fig.  i. 

This  method  was  found  to  be  too  slow  and  to  frequently 
give  inconsistent  results.  It  was  impossible  to  prevent  the  ab- 
sorption of  some  CO,  while  removing  the  crucible  from  the  fur- 
nace for  weighing. 

STATIC  METHOD. 

Dr.  Johnston  then  resorted  to  the  "static  method,"  in  which 
the  dissociation  pressures  are  measured  directly.  A  diagram  of 
the  apparatus  is  shown  in  Fig.  2.  A  platinum  tube,  P,  about  5 
cm.  long  and  4  mm.  inside  diameter,  contained  the  substance. 
This  tube  was  placed  in  a  small  electric  furnace  with  a  thermo- 
couple for  determining  the  temperatures.  A  piece  of  glass  tube, 
C,  was  fused  to  P  and  to  one  arm  of  a  U  tube  which  was  connected 
to  the  barometer.  On  each  arm  of  the  U  tube  was  a  bulb,  D, 
bent  to  the  side  and  holding  enough  mercury  to  fill  the  U-tube 
to  a  depth  of  about  3  cm.  To  prevent  condensation  of  the  vapor 
from  P,  the  U-tube  and  C  were  enclosed  by  a  glass  steam  jacket. 

With  the  mercury  in  bulb  L,  the  apparatus  was  exhausted 
through  A  by  means  of  a  mercury  pump.  Cock  A  was  then  closed, 
and  the  mercury  run  from  L  into  the  U-tube  by  tilting  the  ap- 
paratus. Heating  was  begun,  and  at  the  first  indication  of  pres- 
sure in  P,  the  mercury  in  the  two  arms  of  the  U-tube  was  brought 
to  the  same  level  by  admitting  some  air  at  B  and  adjusting  by 
means  of  the  leveling  tube  R. 

In  his  work  with  calcium  hydroxide,  Dr.  Johnston  slaked 
pure  CaO  and  absorbed  the  excess  water  in  a  desiccator.  An- 
other portion  was  made  by  allowing  the  CaO  to  absorb  moisture 


XOTE    ON    DISSOCIATION    OF    CALCIUM    HYDRATE. 

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21 


slowly  until  the  composition  was  about  CaO  o.8H,0.  In  using 
this  substance,  it  was  found  necessary  to  heat  it  slightly  during 
exhaustion  of  the  apparatus  since  pressures  of  several  cm.  ap- 
peared between  200 °  and  300  °  which  again  disappeared  in  part 
on  further  heating.  These  abnormal  pressures  were  supposedly 
due  to  loosely  combined  or  absorbed  moisture,  and  upon  their 
appearance  the  test  was  stopped  and  the  apparatus  again  ex- 
hausted. Only  such  pressures  were  taken  as  appeared  at  definite 
temperatures  on  heating  and  again  disappeared  on  cooling.  The 
"abnormal  pressures"  disappeared  only  partly  on  cooling.  Un- 
der these  conditions,  it  was  found  advisable  to  use  a  mixture  of 
CaO  and  the  hydroxide,  although  this  did  not  entirely  eliminate 


22 


NOTE    ON    DISSOCIATION    OF    CALCIUM    HYDRATE. 


the  trouble,  which  was  noted  with  all  of  the  hydroxides  studied. 
The  results  of  the  work  on  Ca(OH)2  by  this  method  are  shown  in 
Fig.  3.     By  the  curve,  it  is  seen  that  the  dissociation  pressure 


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reaches  760  mm.  at  a  temperature  of  547  °  C.  Hence  this  is 
taken  as  the  dissociation  temperature  of  the  substance  under 
atmospheric  pressure. 

In  studying  zeolites  Friedel8  heated  them  at  successively 
higher  temperatures  in  a  current  of  air  of  approximately  constant 
vapor  pressure.  This  method  was  adopted  by  Allen  and  Clement9 
in  their  study  of  tremolite,  using  dry  instead  of  moist  air.  A 
crucible  containing  the  material  was  placed  in  an  electric  fur- 
nace, through  which  a  current  of  air,  dried  by  concentrated 
H2S04,  was  passed.  After  heating  for  some  time  at  a  definite 
temperature,  the  crucible  was  quickly  removed  to  a  desiccator, 
cooled  and  weighed.  Heating  was  continued  at  each  tempera- 
ture until  practically  constant  weight  was  obtained.  In  one 
case,  the  experiment  was  repeated  with  moist  air  to  determine 
the  effect  upon  the  results  obtained  by  using  dry  air. 

EXPERIMENTAL  WORK. 

This  method  was  adopted  for  the  present  work.  The  hy- 
drate was  prepared  by  calcining  pure  CaC03  at  10500  C.  and 
slaking  the  oxide  with  a  slight  excess  of  water.  A  portion  of 
the  hydrate  was  placed  in  a  platinum  crucible  and  heated  in  an 


8  Ztschr.  phys.  Chem.,  XXVI,  p.  323. 

9  Am.  Jour.  Sci.,  Vol.  XXVI.  No.  152. 


NOTE    ON    DISSOCIATION    OF    CALCIUM    HYDRATE. 


23 


electric  furnace  in  a  bath  of  dry  air,  free  from  CO,,  at  successive 
temperatures  from  2000  to  7500  C.  at  500  intervals.  At  30-min- 
ute  intervals,  the  crucible  was  removed  from  the  furnace  and  cooled 
in  a  desiccator  over  concentrated  H2S04.  The  heating  was  con- 
tinued at  each  temperature  until  constant  weight  was  reached. 
It  was  impossible  to  prevent  the  absorption  of  some  C02  during 
the  transfer  of  the  hot  crucible  from  the  furnace  to  the  desiccator. 
The  first  loss  of  weight  was  noted  at  400 °  C.  Continued  heating 
at  this  temperature  gave  a  total  loss  of  weight  of  77  per  cent,  of 
the  water  present  above  200  °  C.  At  650 °  another  loss  of  weight 
took  place  amounting  to  22  per  cent.  A  second  trial  was  made 
with  io°  intervals  from  3500  to  4000  C,  and  the  first  loss  was 
found  to  take  place  at  3800  C. 

To  prevent  the  absorption  of  C02  by  the  sample,  a  method 
of  weighing  within  the  furnace  was  adopted.  A  platinum  cru- 
cible was  suspended  in  the  furnace  by  a  fine  platinum  wire  from 
one  pan  of  a  balance  that  was  carefully  protected  from  unequal 
heating  from  the  furnace.  A  thermocouple  was  placed  with  the 
junction  just  under  the  middle  of  the  crucible.  A  current  of 
air,  free  from  C02  and  dried  by  CaCl2  and  P205,  was  circulated 
through  the  furnace.  A  weighed  portion  of  the  hydrate  was 
placed  in  the  crucible  and  dried  at  25  °  C.  The  temperature  was 
then  raised  gradually  until  a  loss  of  weight  began  at  375  °  C. 
It  was  somewhat  surprising  that  there  was  no  loss  of  weight  be- 


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NOTE    ON    DISSOCIATION    OF    CALCIUM    HYDRATE. 


tween  25  °  and  375  °  as  some  mechanically  held  water  might  be 
expected.  After  constant  weight  was  reached  at  375  °,  the 
heating  was  continued  beyond  the  point  noted  by  Johnston. 
The  second  loss  of  weight  took  place  at  5800  C.  The  loss  of  weight 
curves  for  several  trials  are  shown  in  Fig.  4. 

To  determine  whether  the  presence  of  moisture  in  the  fur- 
nace would  have  any  effect  upon  the  results,  the  air  current  was 
saturated  at  0°  to  i°  C.  before  passing  through  the  furnace, 
giving  a  vapor  pressure  of  about  5  mm.  The  loss  of  weight  was 
found  to  occur  at  the  same  points  as  before  but  to  proceed  at  a 
slower  rate.  The  quantitative  results  differ  somewhat,  due 
possibly  to  the  longer  time  required  in  the  latter  trial.  The  re- 
sult of  the  trial  is  shown  in  Fig.  5. 


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The  results  of  these  experiments  indicate  the  existence  of 
two  hydrates  of  CaO,  the  CaO.H20  dissociating  at  375 °  C,  leav- 
ing a  lower  hydrate  which  dissociates  at  5800  C,  leaving  CaO. 
That  the  loss  of  weight  at  each  point  is  due  to  the  dissociation 
of  a  chemical  compound  is  shown  by  the  shape  of  the  curves. 
The  break  is  abrupt  with  no  gradual  slope  preceding  it.  If  me- 
chanical or  dissolved  water  were  being  driven  off,  there  would 
be  a  gradual  loss  of  weight  with  increasing  temperature. 

SUMMARY. 
Various  temperatures  are  given  for  the  dissociation  of  Ca(OH)2 
ranging  from  450 °  by  Le  Chatelier  to  547  °  C.  by  Johnston. 


NOTE    OX    DISSOCIATION-    I  >F    CALCIUM    HYDRATE.  25 

Using  the  "loss  of  weight"  method,  two  dissociation  points 
are  found.  The  hydrate,  Ca(OH)2,  dissociates  at  375 °,  forming 
a  lower  hydrate  that  loses  its  H,6  at  5800  C. 

No  mechanical  water  was  driven  off  above  25 °  C. 

In  conclusion,  the  writer  wishes  to  express  his  indebtedness 
to  Professor  A.  Y.  Bleininger  for  many  valued  suggestions  in  this 
work. 


[Reprinted  from  Transactions  American  Ceramic  Society,     Vol.  XIV, 
by  Permission.] 

NOTE  ON  THE  RELATION  BETWEEN  PREHEATING  TEM- 
PERATURE AND  VOLUME  SHRINKAGE. 

By  R.  K.  Hursh. 

INTRODUCTION. 

An  extended  study  of  the  effect  of  preliminary  heat  treat- 
ment upon  clays  within  a  practical  temperature  range  has  been 
made  by  Professor  Bleininger.1  Especial  attention  was  given  to 
the  effect  upon  the  volume  shrinkage.  A  decided  change  in  the 
properties  of  most  of  the  clays  was  noted  at  temperatures  of  200  ° 
to  300  °  C.  They  became  more  or  less  granular  and  decreased 
markedly  in  plasticity.  There  was  a  material  decrease  in  the 
volume  shrinkage  and  an  increase  in  the  amount  of  pore  water. 
In  a  few  cases,  this  change  occurred  at  somewhat  higher  tempera- 
tures. One  fine-grained,  highly  plastic  clay,  similar  in  behavior 
to  bentonite,  showed  a  considerable  change  in  physical  proper- 
ties at  2500;  but  treatment  at  temperatures  up  to  400  °  failed  to 
reduce  the  shrinkage  to  working  limits. 

Professor  Or  ton,2  in  studying  some  tertiary  clays  which  gave 
trouble  in  drying,  found  ordinary  preheating  temperatures  to 
be  ineffective.  When  the  temperature  was  raised  to  450°-5io° 
C.  the  plasticity  and  shrinkage  were  reduced  sufficiently  to  make 
the  clay  workable.  Under  the  conditions  of  the  tests  the  period 
of  safe  treatment  at  these  temperatures  was  closely  limited  since 
the  clays  lost  their  plasticity  entirely  when  kept  a  little  too 
long  in  the  dryer.  As  some  time  is  required  for  heat  to  penetrate 
the  clay  it  is  possible  that  the  temperature  may  have  reached 
a  higher  point  in  the  longer  treatments  than  was  indicated  by 
the  thermo-couple.  The  test,  however,  represents  the  prac- 
tical conditions  in  a  rotary  dryer. 

EXPERIMENTAL  WORK. 
The  present  work  was  undertaken  with  the  purpose  of  se- 
curing some  further  data  upon  the  effect  of  the  higher  tempera- 
tures of  preheating  upon  the  physical  properties  of  clays  as  in- 
dicated by  changes  in  volume  shrinkage.     Four  clays  were  used: 

1  Bull.  No.  7,  Bureau  of  Standards. 

2  Trans.  A.  C.  S..  Vol.  XIII,  p.  765. 


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PREHEATING   TEMPERATURE    AND   VOLUME    SHRINKAGE.  2Q 

No.  i.  A  plastic,  somewhat  sandy  surface  clay  from  Urbana, 
Illinois. 

Xo.  2.     A  plastic,  red-burning  shale  from  Danville,  111. 

No.  3.  A  plastic,  Xo.  2  fire  clay,  having  a  high  drying 
shrinkage,  from  St.  Louis,  Mo. 

Xo.  4.  A  fine  grained,  weathered  shale  from  Saskatchewan 
similar  in  character  to  the  clays  studied  by  Professor  Orton. 
It  became  very  sticky  in  the  plastic  state  and  cracked  to  pieces 
under  any  conditions  of  drying.  It  is  of  interest  to  note  that  the 
addition  of  1  per  cent,  of  XaCl  greatly  improved  the  working 
properties  and  reduced  the  drying  shrinkage  nearly  one-half. 
It  would  be  possible  by  this  treatment  to  make  commercial  use 
of  the  material. 

The  clays  were  heated  at  temperatures  500  apart  from  2500 
to  650  °  C.  for  three  hours,  from  1  to  2  hours  being  required  to 
reach  the  temperature.  They  were  then  ground  to  pass  20  mesh 
and  made  up  into  small  briquets.  These  were  weighed  and  the 
volumes  measured,  dried  in  air  and  at  no°  in  an  oven,  weighed, 
immersed  in  coal  oil  for  several  hours  and  the  dry  volumes  meas- 
ured. Care  was  taken  to  get  about  the  same  consistency  in  the 
samples  when  making  up  the  briquets.  The  shrinkage  curves 
are  shown  in  Fig.   1  and  the  moisture  content  in  Fig.  2. 

DISCUSSION  OF  RESULTS. 

The  surface  clay,  Xo.  1,  changed  in  color  from  yellow  to 
brown  at  2500  and  to  a  light  salmon-red  at  4000.  The  plasticity 
was  considerably  decreased  at  2500,  was  very  low  at  4000,  the 
briquets  being  very  friable,  and  was  entirely  gone  at  450 °.  The 
color  changes  seem  to  correspond  closely  to  the  changes  in  vol- 
ume shrinkage.  Above  300 °  the  shrinkage  decreased  rapidly  to 
400 °,  beyond  which  the  heat  treatment  had  little  effect. 

The  shale,  No.  2,  changed  from  gray  to  brown  at  3500  and  to 
red  at  4000.  The  plasticity  was  considerably  decreased  at  2000, 
but  decreased  gradually  from  200 °  to  600 °.  At  650  °  no  plasticity 
remained,  and  the  briquets  were  too  fragile  to  handle.  The  shrink- 
age decreases  very  little  from  2000  to  5500  but  drops  considera- 
bly at  600  °. 

The  fire  clay,  Xo.  3,  decreased  in  plasticity  gradually  up  to 


30  PREHEATING   TEMPERATURE    AND   VOLUME    SHRINKAGE. 

400 °,  but  at  450 °  it  became  buff  in  color  and  was  practically 
non-plastic.  The  effect  of  the  heat  treatment  is  much  more 
marked  than  with  the  surface  clay  and  the  shale.  The  shrink- 
age curve  drops  very  abruptly  at  3500.  The  behavior  of  this 
clay  is  similar  to  that  of  an  English  ball  clay  studied  by  Professor 
Bleininger.1 

The  weathered  shale,  No.  4,  changed  in  color  from  gray  to  deep 
maroon  at  3300,  at  which  point  the  cracking  of  the  briquets  was 
noticeably  decreased  but  was  still  very  bad.  Cracking  decreased 
gradually  beyond  this  temperature,  but  the  briquets  at  5500 
were  the  only  ones  that  remained  sound  with  open-air  drying. 
The  sticky  quality  of  the  clay  was  retained  up  to  5000.  At  5500 
it  was  quite  granular  but  developed  considerable  plasticity  with 
wedging.  The  effect  of  the  heating  treatment  upon  the  shrink- 
age is  more  pronounced  than  with  the  other  clays,  but  an  ab- 
normally high  shrinkage  remains  500 °.  Beyond  this  point  the 
drop  in  the  curve  is  so  abrupt  that  very  careful  temperature  con- 
trol would  be  necessary  in  obtaining  a  sufficient  reduction  in 
shrinkage  to  prevent  cracking  without  destroying  the  working 
properties.  From  the  high  temperature  required  and  the  narrow 
range  of  safe  heat  treatment,  it  is  obvious  that  preheating  would 
not  be  a  safe  method  for  practical  use  with  such  a  clay. 

The  effect  of  the  heat  treatment  upon  these  clays  is  quite 
different.  The  shale  is  most  gradually  affected,  losing  its  plas- 
ticity entirely  only  at  temperatures  above  red  heat.  It  is  proba- 
ble that  this  is  characteristic  of  the  more  homogeneous  materials. 

The  fire  clay  shows  an  abrupt  drop  in  its  shrinkage  curve, 
behaving  similarly  to  other  fire  clays  and  a  certain  ball  clay. 

The  fourth  clay  has  such  abnormally  high  shrinkage  that 
only  treatments  above  500 °  C.  would  suffice  to  eliminate  crack- 
ing in  drying.  It  is  evident  that  clays  of  this  type  are  not  adapted 
to  preheating  treatment. 


UNIVLRSITY  OF  ILLINOIS  BULLLTIN 


Vol.  X.  5LPTEMBLR  23,  1912.  No.  4 


[Entered  February  14,  1902,  at  Urbana,  Illinois,  as  second-class  matter  under 
Act  of  Congress  of  July  16,  1894.] 


BULLETIN  No.  18 
DEPARTMENT  OF  CLRAMIC5 

A.  V.  BLLININGER,  Director 


A   THERMAL   5TUDY    OF     BORIC     ACID-5ILICA 

MIXTURL5 

BY 
A.  V.  BLFJNlNGtR  AND  PAUL  TE.LTOR 


THL  RLPLACLMLNT  OF  TIN  OXIDL  BY  ANTIMONY 
OXIDL  IN  LNAMLLS  FOR  CA5T  IRON 

BY 
R.  L.  BROWN 


1911-1912 


PUBLISHED  FORTNIGHTLY  BY  THL  UNIVERSITY 


[Reprinted  from  Transactions  American  Ceramic  Society.     Vol.  XIV, 
i«v  Permission.] 

A  THERMAL  STUDY   OF   BORIC   ACID-SILICA  MIXTURES. 

By  A.  V.  BlEininger  and  Paul  Teetor,  Urbana,  111. 

The  subject  of  possible  chemical  combinations  of  silica 
and  boric  acid  has  received  some  attention  in  our  Transactions,1,2 
and  the  question  raised  is  interesting  inasmuch  as  such  mixtures 
possess  most  decidedly  the  character  of  glasses  or  solid  solutions. 
Thermal  analysis  thus  does  not  promise  a  fruitful  field  of  in- 
vestigation. However,  of  the  two  methods  comprising  thermal 
analysis,  the  determinations  of  the  softening  temperatures  is  of 
some  interest  in  itself,  since  it  gives  us  the  general  character 
of  the  fusion  curve  of  the  two  components  involved. 

A  thermal  lag  is  not  to  be  expected  either  in  the  heating 
or  cooling  curves.  In  the  present  work,  a  search  was  made,  how- 
ever, for  such  a  point  based  on  the  statement  of  Binns,  Trans. 

A.  C.  S.,  X,  p.  158,  in  which  he  records  a  temperature  increase 
upon  the  fusion  of  a  mixture  of  boric  acid  and  silica,  due  to 
some  exothermal  change.  The  present  research  deals,  (a)  with  the 
determination  of  the  softening  points  of  Si02-B20:f  mixtures  be- 
tween the  limits  B203-B,03.3Si02,  (b)  with  the  determination 
of  heating  and  cooling  curves  and  (c)  with  an  investigation  of  the 
solubility  of  the  fused  glasses  in  water.  The  reagents  used  were 
chemically  pure  hydrous  boric  acid  and  silica,  the  latter  being  a 

B.  &  A.  preparation  which  unfortunately  contained  several  per 
cent,  of  sodium  chloride  and  water.  In  the  latter  part  of  the 
series,  fusions  were  made  also  with  flint  which  had  been  passed 
through  a  200  mesh  sieve.  The  calculation  of  the  mixtures 
was  based  upon  the  analyzed  silica  content,  practically  97  per 
cent.  The  boric  acid  was  fused,  cooled  rapidly  and  kept  in  a 
desiccator.  It  was  crushed  in  a  porcelain  and  pulverized  in  an 
agate  mortar.  Similarly,  the  silica  was  ignited  and  kept  in  a 
desiccator.  The  mixtures  were  ground  together  in  the  agate 
mortar  and  fused  over  the  blast  lamp  in  a  10  cc.  platinum  crucible 
kept  covered  during  the  heating.  After  some  time,  the  yellow 
color  of  the  mass  disappeared,  which  seemed  to  be  a  measure 
of  the  completeness  of  the  fusion.     The  cooled  mass  had  an  opaque 


1  Binns.  Trans.  A.  C.  S..  Vol.  X.  p.   158. 

2  Singer,  Trans.  A.  C  S..  Vol.  XI.  p.  676. 


4  A  THERMAL  STUDY  OF  BORIC  ACID-SILICA  MIXTURES. 

but  glassy  appearance.  The  fused  mixture  was  easily  removed 
from  the  crucible  by  inserting  a  platinum  rod  and  quickly  cooling 
in  cold  water.  Then  the  fusion  was  pulverized  and  screened 
through  80  and  150  mesh  screens.  The  portion  passing  the  80 
but  remaining  on  the  150  mesh  screen  was  used  for  the  solubility 
samples.  This  was  done  in  order  that  no  great  variations  in 
the  surface  factor  might  affect  the  solubility  of  the  several  mix- 
tures. 

SOFTENING  POINT  DETERMINATION. 

For  this  purpose,  the  fused  mixtures  of  SiO,  and  B203, 
ground  to  a  fine  powder,  were  made  up  with  a  little  water  into 
small  cones,  and  placed  in  an  electric  resistance  furnace.  The 
specimens  were  kept  in  position  by  means  of  platinum  foil.  Since 
in  glasses  practically  no  other  criterion  is  available  than  the 
deformation  point,  the  temperature  at  which  the  cones  bent  was 
taken  to  represent  the  softening  point.  Care  was  taken  to  raise 
the  heat  at  a  regular  rate  by  rheostat  regulation,  and  the  tempera- 
ture readings  were  made  by  means  of  a  Pt-PtRd  thermo-couple, 
the  electromotive  force  of  which  was  determined  by  the  method 
of  balancing  against  a  standard  cell  by  means  of  a  potentiometer 
indicator. 

Owing  to  the  fact  that  by  mistake  water  was  used  in  making 
up  the  mixtures,  some  anhydrous  boric  acid  reverted  to  the 
hydrous  form.  This,  of  course,  made  it  troublesome  to  determine 
the  deformation  point  of  B20:!  owing  to  the  evolution  of  steam 
and  the  resulting  bubbling.  With  the  addition  of  0.1  Si02, 
the  cones  seemed  to  stand  up  apparently  in  good  shape.  The 
heat  given  off  on  adding  water  to  the  B203.i.5Si02  mixture 
was  so  great  that  the  crucible  could  not  be  held  in  the  hand. 
At  the  same  time  very  little  heat  was  evolved  by  the  B203.i.4Si02 
and  the  B203.i.6Si02  glasses.  On  fusing  the  B203.i-5Si02  mix- 
ture, it  assumed  a  pink  color. 

It  was  soon  observed  that  these  glasses  were  quite  viscous. 
This  was  illustrated  by  the  fact  that  a  twisted  platinum  wire  on 
being  lowered  into  the  fused  mass  and  again  raised  was  found  to 
draw  out  a  ribbon  of  glass.  It  is  not  surprising,  therefore,  that 
the  softening  points  could  not  be  checked,  in  spite  of  the  fact 
that  the  same  rate  of  heating  was  followed  as  closely  as  possible. 


A  THERMAL  STUDY  <  >!•'  BORIC  ACID-SILICA  MIXTURES.  5 


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6  A  THERMAL  STUDY  OF  BORIC  ACID-SILICA  MIXTURES. 

In  going  over  this  part  of  the  work  four  times,  the  results  shown 
in  Fig.  i  were  obtained.  The  softening  points  of  the  mixtures 
beyond  B203.2Si02  are  not  plotted  since  the  divergence  in  this 
part  of  the  series  is  still  greater. 

Softening  point  determinations  were  also  made  upon  rods 
drawn  from  all  of  the  fusions  but  these  likewise  gave  extremely 
variable  results,  considerably  lower  than  those  obtained  for  the 
cones. 

The  evidence  thus  far  collected  makes  it  apparent  that  any 
reaction  taking  place  under  these  conditions  would  be  greatly 
hindered  by  the  internal  molecular  friction. 

HEATING  AND  COOLING  CURVES. 
A  considerable  number  of  heating  and  cooling  curves  were 
determined  with  special  reference  to  the  B203.2Si02  mixture. 
The  latter  was  prepared  from  fused  B203  and  prepared  Si02,  and 
from  fused  boric  acid  and  flint,  passed  through  the  200  mesh 
sieve.  In  no  instance  was  there  a  temperature  acceleration  or 
lag  observed,  and,  hence,  the  observation  of  Binns  was  not  checked. 
In  Fig.  2,  the  heating  curve  in  which  the  couple  readings  were 
made  by  means  of  a  potentiometer  indicator  is  shown.  The 
junction  was  kept  at  o°C.  by  means  of  ice.  In  Figs.  3  and  4, 
both  the  heating  and  cooling  curves  for  prepared  silica  and  flint 
mixtures  as  indicated  by  a  Siemens  and  Halske  recorder,  making 
a  contact  every  16  seconds,  are  presented.  It  was  observed 
that  on  fusing  any  mixture  of  B203  and  Si02,  without  previous 
fritting,  some  vapor  was  expelled  suddenly,  carrying  evidently 
a  certain  amount  of  boron.  This  happened  also  when  both  the 
boric  acid  and  silica  had  been  ignited  separately  to  constant 
weight  before  mixing.  Since  Professor  Binns  used  an  optical 
pyrometer,  it  is  quite  possible  that  by  focusing  upon  this  vapor 
the  readings  were  changed  as  observed  by  him. 

SOLUBILITY  DETERMINATIONS. 
The  different  mixtures  were  fused  and  pulverized  on  cooling. 
The  resulting  powder  was  screened  through  the  80  and  150  mesh 
sieve.  All  material  coarser  than  the  80  and  finer  than  the  150 
mesh  was  rejected.  One  gram  samples  were  then  weighed  and 
put  in  stoppered  250  cc.  Erlenmeyer  flasks.     These  were  placed 


A  THERMAL  STUDY  OF  BORIC  ACID-SII.ICA   MIXTURES.  7 


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A  THERMAL  STUDY  OF  BORIC  ACID-SILICA  MIXTURES. 


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A  THERMAL  STUDY  OS   BORIC  ACID  SILICA   MDCTUSBS.  9 

in  a  shaking  machine  together  with  200  cc.  of  distilled  water. 
After  shaking  for  10  hours  and  standing  over  night,  the  liquid 
was  filtered  off  and  the  residue  washed.  Then  200  cc.  of  water 
was  again  added  (including  the  wash  water  used)  and  the  flasks 
were  again  shaken  for  one  hour.  The  residue-  was  again  filtered 
and  washed.  After  drying,  the  residues  and  paper  were  ignited 
and  the  weights  determined.  The  insoluble  matter  in  each  case 
was  brushed  off  and  the  paper  burnt  separately. 

The  weights  of  the  residues  are  shown  in  the  curve  of  Fig.  5. 


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It  is  seen  that  all  of  the  boric  acid  was  dissolved  in  the  first  of 
the  series  as  well  as  some  of  the  silica.  At  a  point  close  to 
B203.i.8SiO;,,  however,  the  solubility  curve  crosses  the  line 
indicating  the  percentage  content  of  B203  (shown  by  the  dotted 
line)  which  proves  that  some  B,03  has  been  rendered  insoluble. 
This  tendency  increases  with  the  silica  content.  At  the  molecular 
ratio  1:2a  decided  drop  occurs  indicating  the  rapid  formation  of 
an  insoluble  glass.  As  to  the  cause  of  this  sudden  change,  we 
can  only  conjecture  at  the  present  time.  To  establish  the  fact 
that  a  chemical  combination  has  taken  place  would  require  the 


IO  A  THERMAL  STUDY  OF  BORIC  ACID-SILICA  MIXTURES. 

running  of  a  parallel  series  using  another  criterion  such  as  the 
specific  gravity  of  the  powder.  At  the  present  time,  however, 
this  evidence  might  be  used  to  support  the  claim  that  we  are 
dealing  here  with  a  solid  solution  representing  a  chemical  union 
between  the  silica  and  the  boric  acid. 

CONCLUSIONS. 

Fused  boric  acid-silica  mixtures  are  typical  glasses  pos- 
sessing no  definite  deformation  temperatures. 

No  thermal  phenomena  were  observed,  i.  c,  there  was  no 
absorption  or  liberation  of  heat  throughout  the  series  B203  to 
B203.3Si02. 

Boric  acid  when  fused  with  silica  first  dissolves  some  of 
the  latter.  The  amount  of  matter  soluble  in  water  decreases 
somewhat  more  rapidly  than  the  B203  content.  Between  2  and 
2.2  Si02  a  decided  drop  in  the  solubility  of  the  glasses  occurs, 
indicating  that  some  B203  has  been  rendered  insoluble.  It  is 
quite  probable,  although  not  proven,  that  a  chemical  combina- 
tion might  take  place  at  this  point.  The  gradual  decrease  in 
solubility  might  thus  be  ascribed  to  the  formation  of  some  of 
this  combination  at  an  earlier  stage.  At  the  point  mentioned, 
a  more  rapid  enrichment  would  thus  take  place. 

DISCUSSION. 
Professor  Binns:  I  am  interested  in  the  results  secured  by 
Professor  Bleininger.  When  I  made  the  first  experiments  of 
this  kind  I  expressly  disclaimed  any  pretension  to  the  ability 
called  for  by  such  work,  and  I  based  my  chief  claim  as  to  the 
action  of  boron  upon  the  practical  issues  as  expressed  in  glaze 
composition.  From  this  position,  which  has  been  confirmed 
by  Dr.  Singer  and  Mr.  Stull,  I  have  not  had  cause  to  retreat. 


[Reprinted  from  Transactions  American  Ceramic  Society,      Vol.  XIV. 
by  Permission.] 

THE  REPLACEMENT  OF  TIN  OXIDE  BY  ANTIMONY  OXIDE 
IN  ENAMELS  FOR  CAST  IRON.1 

By  R.  E.  Brown,  Mt.  Savage,  Md. 

INTRODUCTION. 

Classification  of  Opacifiers. — Opacifiers  for  the  purposes  of 
this  work  are  divided  into  two  classes:  (i)  partial  opacifiers, 
and  (2)  absolute  opacifiers. 

In  the  first  class  are  included  bone  ash,  fluorite,  cryolite, 
and  silica.  Bone  ash  is  rarely  employed  in  enamels,  but  the  re- 
maining three,  especially  the  silica,  are  invariably  used.  Fluorite 
and  cryolite  are  advantageous,  commercially,  both  from  the 
standpoint  of  their  low  fusibility  and  their  fluorine  content. 
The  latter  gives  them  the  property  of  acting  as  weak  opacifiers, 
thereby  decreasing  the  amount  of  absolute  opacifier  needed.2 
The  silica,  as  is  shown  by  the  following  work,  has  no  opacifying 
tendencies  in  itself  in  this  type  of  glasses  but  emphasizes  and  in- 
creases the  opacity  brought  about  by  certain  opacifiers  proper. 

In  the  second  class,  the  opacifiers,  per  se,  are  arsenious  oxide, 
zirconium  oxide,  tin  oxide  and  antimony  oxide.  Arsenious 
oxide  finds  a  very  limited  use,  being  employed  only  for  decorative 
work  on  jewelry  and  art  ware.  Zirconium  oxide  is  not  widely 
used;  while  some  consider  it  too  expensive  for  commercial 
work,  others  regard  it  a  cheap  opacifier  as  a  substitute  for  tin 
oxide.3  Tin  oxide  is  by  far  the  most  widely  used  of  the  opacifiers, 
and  is  employed  not  only  in  the  enameling  of  sheet  iron  and  cast 
iron,  but  in  the  enameling  of  clay  products  as  well. 

Antimony  oxide  has  had,  to  date,  only  an  extremely  limited 
use  as  an  opacifier.  It  has  been  used  to  some  extent  in  Ger- 
many in  conjunction  with  zinc  oxide  as  a  substitute  for  tin  oxide.4 
It  has  been  used  in  this  country  to  some  extent,  and  in  one  case 
its  use  in  conjunction  with  other  ingredients  is  patented  as  "a 
substitute  for   tin   oxide."5     In   a   "Note   on   White   Antimony 


1  Abstract  of  a  thesis  fulfilling  part  of  the  requirements  for  the  degree  of  Bachelor  of 
Science  in  Ceramics,  University  of  Illinois. 

2  Mayer  and  Havas,  Sprechsaal,  XLII.  460-461. 

3  La  Ceramique.  11,   100-101.     Keram  Rundschau,  XVI,  89-91,   135-139. 
*  Ph.  Eyer.  Stahl  und  Eisen,  XVIII,  1097,  1099. 

5  U.  S.  Patent,  932,839. 


12       REPLACEMENT    OF   TIN    OXIDE    IN   ENAMELS   FOR    CAST    IRON. 

Enamels,"  Bock  points  out  the  dangers  of  the  use  of  antimony 
oxide  in  enamels  for  cooking  vessels,  but  no  mention  is  made  of 
its  employment  in  enamels  for  cast  iron.6 

The  most  expensive  constituent  of  the  ordinary  commercial 
enamel  is  the  opacifying  agent,  tin  oxide,  both  by  reason  of  the 
high  market  price  and  the  quantity  employed.  The  prices  of 
antimony  oxide  and  tin  oxide  in  barrel  lots  are  at  present  io1/2 
and  45  cents  per  pound,  respectively. 

Object  of  Work. — It  was  with  a  view  to  using  the  cheaper 
opacifier  for  cast  iron  enamels  that  this  work  was  undertaken. 
The  work  attempts  to  determine,  in  a  practical  way,  the  con- 
ditions under  which  antimony  oxide  may  be  used  in  enamels. 

EXECUTION  OF  WORK. 

Preparation  of  the  Enamels. — In  carrying  out  a  series  the 
ingredients  of  the  two  extremes  of  a  series  were  weighed  up  and 
mixed  thoroughly  by  passing  5  or  6  times  through  a  20  mesh 
screen.  The  batch  was  next  put  into  a  small  fire  clay  crucible 
(capacity  about  250  grams  of  the  raw  batch)  and  fritted  in  a  pot 
furnace,  fired  by  a  blast  lamp  using  artificial  gas  and  compressed 
air  as  fuel.  After  melting  and  becoming  relatively  free  from 
bubbles  the  contents  were  poured  into  water.  It  was  then  dried, 
again  put  into  the  crucibles  and  refritted,  care  being  taken  in 
this  second  fritting  to  prolong  the  heating  to  such  length  of  time 
that  no  bubbles  were  given  off.  As  soon  as  bubbles  had  ceased 
to  form,  the  contents  were  again  quenched  by  pouring  into  water. 
The  shattered  glass  was  dried  and  then  ground  in  8  inch,  porcelain, 
ball  mills  so  as  to  pass  a  200  mesh  sieve. 

The  two  extremes  of  a  series,  now  in  a  powdered  form, 
were  weighed  out  in  the  proper  proportions  to  form  the  inter- 
mediate enamels.  These  were  now  mixed  by  rubbing  5  or  6 
times  through  a  60  mesh  sieve. 

The  Ingredients. — The  raw  ingredients  employed  in  intro- 
ducing the  following  constituents  with  the  molecular  weights 
used  were  as  follows : 

ZnO:     Introduced  as  zinc  oxide  (81). 

PbO :     Brought  in  as  red  lead  Pb304  (685) . 


Chem.  Ztg..  XXXII,  516-517. 


REPLACEMENT   OF   TIN    OXIDE    IN    ENAMELS   FOR    CAST    [RON.      I  3 

BaO:  Where  employed,  was  brought  in  by  barium  car- 
bonate (197). 

CaO:  Brought  in  by  lluorite  (78),  whiting  (100),  and 
hydrated  lime  (74). 

Na20:  Introduced  as  sodium  carbonate  (106),  borax  (382), 
and  cryolite  (210). 

K,0:  Brought  in  by  potassium  nitrate  (101)  and  potash 
feldspar  (557). 

MgO:  Brought  in  by  magnesium  carbonate  (84)  and 
magnesium  oxide  (40). 

A1203:  Potash  spar  (557)  was  used  as  the  main  source  of 
alumina.  Small  amounts  of  cryolite,  Na3AlF6  (210)  were  also 
used. 

B203 :  This  was  brought  in  by  using  borax  (382)  in  the  cover 
enamels  and  as  borax  and  boric  acid  (62)  in  the  ground  coats. 

SnO,:     Brought  in  as  tin  oxide  (150). 

Sb,03:     Introduced  as  white  oxide  of  antimony  (288). 

Si02:     Brought  in  as  potash  feldspar  (557),  and  as  flint  (60). 

In  addition  to  the  above  ingredients,  ammonium  carbonate 
was  used  in  some  of  the  enamels  of  the  later  series.  This 
volatilizes  readily  and  serves  as  a  clarifier  of  bubbles  in  the  glass 
during  fritting. 

Trial  Pieces. — The  trial  pieces  were  small  circular  discs 
1/8"  thick  and  2"  in  diameter  with  a  raised  center.  The  iron 
used  for  casting  these  trials  did  not  prove  to  be  of  a  very  satisfac- 
tory grade  as  it  frequently  produced  large  bubbles  or  blisters  in 
the  enamels,  probably  due  to  the  sulphur  content  of  the  iron. 

The  trials  were  cleaned  by  pickling  for  20-30  minutes  in  a 
dilute  solution  of  hydrochloric  acid  so  as  to  remove  the  scale 
and  any  oxide  present.  After  this  they  were  washed  and  scrubbed 
and  then  dipped  in  a  dilute  solution  of  sodium  carbonate  so  as  to 
neutralize  all  of  the  acid.  They  were  then  scrubbed  and  washed 
again,  the  surface  water  was  wiped  off,  and  the  trials  were  put. 
into  a  warm  oven.  Even  with  this  seemingly  thorough  treat- 
ment, the  coat  of  carbon  (left  by  dissolving  the  iron)  was  not; 
entirely  removed,  and  hence  gave  rise  to  bubbles  during  the  burn- 
ing process.  Another  method  of  cleaning  the  iron,  used  in  the 
latter  part  of  the  work,  proved  very  effective.     In  this,  the  iron 


14     REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS    FOR    CAST    IRON. 

was  pickled  as  before  and  then  put  into  a  ball  mill  with  sand  and 
water;  thus  all  of  the  carbon  was  effectually  removed  with  the 
result  that  less  trouble  as  regards  bubbling  was  experienced. 

The  ground  coat  was  applied  to  the  trials  by  dipping,  care 
being  taken  to  secure  a  thin  coat  that  was  as  uniform  as  possible. 

Composition  of  the  Ground  Coat. — -The  ground  coat  chosen 
was  of  the  composition  shown: 

o . 30    K20 

0.24    Na20      lo.297Al.P3 

\  2  .  19  Si02 
0.31  B203     J 


o. 159  CaO 
0.219  MgO 
0.081  PbO 


Batch    weights:     15    flint;    30   potash   feldspar;    10   boric    acid; 

5  KN03;  5  Pb304;  2.2  Ca(OH)2;  2.3  MgO;  10. o  cryolite;  1.0 
fluorite. 

The  trial  piece,  after  being  slush  coated  and  dried,  was 
placed  in  the  furnace,  which  had  been  heated  to  the  temperature 
of  burning.  As  soon  as  the  iron  had  attained  a  sufficient  heat 
for  fusing  the  ground  enamel,  it  appears  to  "melt"  not  unlike 

6  coat  of  frost  or  snow.  This  commences  at  one  spot  and  soon 
has  extended  over  the  whole  trial.  The  trial  now  has  a  glossy 
^appearance.  Almost  coincident  with  this,  innumerable  bubbles 
are  formed  which  "break"  at  once.  This  continues  for  a  short 
time,  after  which  the  glossy  coating  or  glass  smooths  down. 
It  is  at  this  point,  in  the  writer's  judgment,  that  the  burning  of 
the  ground  coat  is  complete.  If  the  trial  is  not  removed  at  once, 
larger  bubbles  are  formed,  but  the  glass  is  then  decidedly  more 
viscous  than  when  the  preliminary  bubbles  were  formed.  When 
they  break,  if  they  break  at  all,  they  leave  a  rough  slag  on  the 
surface  of  the  trial  as  is  shown  by  cooling  the  trial  piece. 

Burning  the  Enamels. — The  furnace  used  for  the  enameling 
was  of  the  open-fired  type,  i.  e.,  without  a  muffle  chamber,  and 
was  fired  by  the  use  of  artificial  gas  and  compressed  air  as  fuel. 
Although  this  is  not  the  type  of  furnace  best  suited  for  this  kind 
of  work,  it  was  the  only  one  available  and  there  was  no  time  for 
the  construction  of  a  more  suitable  one.  The  temperature  of 
burning  was  measured  by  a  Le  Chatelier  pyrometer,  the  couple 
of  which  was  inserted  so  that  its  junction  point  was  at  the  side 


REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS    I<<  >R    CAST    [RON.       1 5 


of  the  trial.  The  holder  for  the  trial  piece  consisted  of  a  bar  of 
iron  "upset"  at  one  end  and  so  shaped  as  to  fit  on  the  inside  of 
the  trial  piece. 

Series  I. 

REPLACEMENT     OF     TIN    OXIDE     BY     ANTIMONY     OXIDE    IN    A    TIN 

ENAMEL. 

This  series  was  carried  out  by  replacing  the  tin  oxide  in  an 
enamel  similar  to  that  given  by  Riddle  in  his  "Types  of  Enamels 
for  Enameling  Cast  Iron  Sanitary  Ware,"  Trans.  A.  C.  S.,  Vol. 
IX,  with  antimony  oxide,  thus: 

0.25  Na20 
o.  10  MgO 
0.15  PbO 
0.15  BaO 
0.15  K20 
0.05  ZnO 
0.15  CaO 

Batch  formulae  (in  equivalents). 


0.15  A1203  ]   i.ooSiO, 

o .  20  B,03   J  o .  1 5  vSn02-o .  075  Sb203 


No. 

O 
u 
a 

■0 

0 

CJ 
d 

pq 

fa 

O 

O 

a 

N 

O 
O 
M 

u 

0 

pa 

a 
to 

E 

c 
to 

0 

0.15 
0.15 
0.15 
0.15 
0.15 

0.05 
0.05 
0.05 
0.05 
0.05 

0.15 
0.15 
0.15 
0.15 
0.15 

O.I5 

O.I5 
O.I5 
O.I5 
O.I5 

O.O5 
O.05 
O.O5 

O.O5 
O.05 

0. 10 
0. 10 
0. 10 
0. 10 
0. 10 

0. 10 
0. 10 
0. 10 
0. 10 
0. 10 

0.15 
0.15 
0.15 
0.15 
0.15 

0. 10 
0. 10 
0. 10 
0. 10 

0 .  10 

0.15 

0. 1125 

0.075 

0.0375 

0.00 

O   Ol88 

3 

4 

5 

0-0375 
O.O56 

O.075 

Description  of  Trials.^ — No.  i  is  a  good  enamel  and  is  a 
typical  tin  enamel.  All  of  the  rest  of  the  series,  with  the  possible 
exception  of  No.  2,  are  very  poor.  A  peculiar  "puckery"  or 
matte  texture  exists,  the  surface  is  rough  and  uneven,  and  the 
enamel  flies  off  in  patches,  resembling  shivering  of  clay  ware. 
In  the  trials  of  enamels  3  and  4,  the  "puckery"  effect  is  partially 
overcome  by  laising  the  burning  temperature.  The  shivering 
is  also  lessened  by  this  treatment.  It  is  also  evident  in  this 
series  as  well  as  in  the  rest  of  the  work  that  where  an  enamel  is 
applied,  too  thick  shivering  is  more  likely  to  occur. 

Thinking  perhaps  that  the  "puckery"  effect  might  be  over- 
come partially  by  making  a  more  easily  fusible  enamel  it  was 


1 6    REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS   FOR   CAST    IRON. 


decided  to  run  a  series  with  a  more  fusible  RO  combination. 
It  was  also  suggested  that  the  "puckery"  effect  might  be  due 
to  the  barium  which  reacted  with  the  sulphur  present  in  the 
Sb203.7  Some  of  the  Sb203  was  tested  and  found  to  contain 
sulphur. 

A  series  embodying  the  two  above  ideas  was  accordingly 
carried  out  as  given  below.  Although  it  was  not  conducted 
strictly  on  a  scientific  basis  it  is  sufficient  to  show  in  a  practical 
way  the  desired  effect. 

Series  II. 

VARIATION     OF     BARIUM     OXIDE     AND     ITS     EFFECT     ON     ANTIMONY 

OXIDE. 


0.25-0.54  Na20 
o.  10-0.00  MgO 
o.  15-0'.  15  PbO 
o.  15-0. 16  K20 
0.05-0.05  ZnO 
o. 15-0. 10  CaO 
o.  15-0.00  BaO 


o.  15-0. 16  Al2Os 
o.  20  B90, 


1 .00  Si02 
0.075  Sb203 


Batch  formulae  (in 

equivalents). 

6 

0 
0 

13 
V 

0 

u 

a 

as 
O 

O 
a 

N 

O 
•z 
M 

+J 

"o 
>> 
u 

0 

K 
O 

Bi 
O 

X 

CS 
Ih 

0 

pq 

O 
u 
at 

1-1 

as 
» 

3     0 

I 

2 

3 

4 

O.15 
O.21 
O.29 
0-35 

0.05 
0.05 
0.05 
0.05 

0.15 
0. 10 

0.05 
0.00 

O.15 
O.  IO 
O.05 
O.OO 

0.05 
0.05 
0.05 
0.05 

0.00 
0.02 
0.04 
0.06 

0.00 
0.02 
0.04 
0.06 

O.OO 
O.O3 
O.O7 
O.  IO 

0. 10 
0. 10 
0. 10 
0. 10 

0.  IO 
0.07 

0.03 

0.00 

O.I5 
O.  148 
O.136 
O.13 

0. 10 
0.14 
0.18 
0.22 

0.075 
0.075 
0.075 
0.075 

Description  of  Trials. — The  "puckery"  effect  has  decreased 
toward  the  end  of  the  series  which  contains  no  barium  and  in 
No.  4  is  not  present  at  all.  This  enamel  is  a  fair  enamel  which 
adheres  well.  No.  1  is  somewhat  shivered.  This  series  shows 
from  a  practical  standpoint  that  barium  should  not  be  used  to 
any  very  large  extent  in  an  enamel  where  there  is  a  contact  with 
sulphur  gases.  Its  use,  however,  in  enamels  where  tin  is  used  as 
an  opacifier  is  very  much  desired,  owing  to  its  ability  to  decrease 
shivering. 


7  Sb203  is  prepared  from  stibnite,  SD2S3,  by  roasting  in  air,  hence  sulphates  are  formed 
which,  if  not  entirely  removed,  would  combine  with  the  barium  compounds. 


REPLACEMENT   OF  TIN    OXIDE    IX    ENAMELS    POS    CAST    IRON.    1 7 


Series  III. 

VARIATION    OF   THE    SILICA    CONTEXT. 

This  series  was  varied  between  the  limits  of  1.00  and  2.00 
•equivalents  of  silica  as  shown : 


o.  10  CaO 
o .  54  Na20 
0.15  PbO 
o.i6K,0 
0.05  ZnO 


0.16  ALA, 
0.20  BX), 


1 .00-2  .00  SiO, 


0.075  Sb203 


Batch  formulae  (in 

equivalents). 

0 

O 
0 

S 
S3 

■d 

3 

V 

pi 

O 
a 

N 

O 

V 

"3 
>> 

H 

u 

x         3 

S         0 

a            n 

a             a 

0 
JS 

2 

3 

4 

5 

6 

7 

8 

9 

o-35 
0-35 
o-35 
o.35 
o.35 
o-35 
o-35 
o-35 
o-35 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

O.05 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 

0. 10 

0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 

0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 

0.22 

o.345 
0.47 

o.595 

0.72 

0.845 

o.97 
1  095 
1 .  22 

0.075 
0.075 
0.075 
0075 
0075 
0.075 
0.075 
0.075 
0.075 

Description  of  Trials. — Nos.  1,  2  and  3  have  an  egg  shell- 
like texture  but  otherwise  are  fair  enamels.  The  trials  of  enamels 
Nos.  4  and  5  are  better  and  do  not  show  the  above  texture  to  such 
a  degree.  No.  6  is  a  fair  enamel  but  is  a  trifle  dull.  No.  7  is  a 
good  enamel  and  adheres  well.  It  is  whiter  and  has  a  better 
gloss  than  the  average  commercial  enamel.  Enamel  No.  8  is 
whiter  than  No.  7  and  has  a  better  gloss.  A  few  of  the  trials 
shiver  somewhat,  showing  that  the  silica  is  a  trifle  too  high. 
Enamel  No.  9  has  shivered  still  more,  but  on  the  trials  where 
it  held,  it  is  the  whitest  and  most  brilliant  of  the  series.  Enamels 
Nos.  8  and  9  have  an  exceptionally  white  color  and  are  more  than 
the  equal  of  the  average  tin  enamel  in  this  respect. 

The  result  of  this  series  seems  to  show  that  the  last  two 
enamels  are  too  high  in  silica  and  also  that  a  silica  content  of 
over  1.85  equivalents  is  conducive  in  shivering.  The  burning 
temperature  rises  as  the  silica  content  increases;  but  this  heat, 


1 8    REPLACEMENT   OF   TIN    OXIDE    IN   ENAMELS   FOR   CAST    IRON. 


even  with  the  enamels  containing  2.0  Si02,  did  not  cause  the  iron 
to  deteriorate  to  any  visible  extent.  As  silica  increases,  the 
whiteness  is  increased,  and  it  is  evident  that  a  sacrifice  must  be 
made  of  part  of  the  whiteness  in  order  to  obtain  enamels  that 
do  not  shiver. 

Series  IV. 

VARIATION   OF   ALUMINA. 
This  series  was  run  between  the  limits  of  0.1  and  0.2  equiv- 
alent of  A1203.      To  bring  in  the  A1203  in  combined  form,  i.  e., 
as  spar,  it  was  necessary  to  change  the  RO  with  respect  to  K20 
and  Na,0  thus: 


o .  1 6-0 .  20  K20 

0.15  PbO 

o . 10  CaO 

o .  54-0 .  50  Na20 

0.05  ZnO 


o .  10-0 .  20  ALO,  I   1 .  80  SiO, 


0.20  B,0, 


0.075  Sb203 


Batch  formulae  (in  equivalents). 

6 

O 
u 

•0 
ca 
a 

.J 

O 
a 

N 

0 
0 

0 
M 

0 
>, 
u 
u 

X 
O 

a 

X 
a 
u 

0 

pq 

u 

a 
a 

M 

■!-> 

a 

d 

1.  .  .  . 

2.  .  .  . 

3 

4 

5 

6 

o-35 

0.342 

0-334 
0.326 
0.318 
0.31 

O.05 
O.05 
O.05 
O.05 
O.05 
O.05 

O.O5 
O.O5 
O.O5 
O.O5 
O.O5 
O.O5 

0.06 
0.049 

0.038 
0.025 
0.013 

0.00 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

O.IO 
O.IO 

0.16 

O.IO 
O.IO 
O.IO 

O.IO 
O.IO 
O.IO 
O.IO 
O.IO 
O.IO 

0.07 
0.09 

O.I  I 

0.13 
0.15 

0.17 

1.38 
1.26 
1. 14 
1.02 
0.90 
0.78 

0.075 
O.O75 
O.O75 
O.O75 
O.O75 
O.O75 

Description  of  Trials. — All  enamels  of  the  series  are  good 
enamels  with  whiteness  increasing  toward  No.  6,  i.  e.,  with  in- 
crease of  A1203.  The  temperature  required  for  maturing  increases, 
however,  with  the  A1203.  The  best  enamel  of  the  series,  taking 
burning  temperature,  whiteness,  gloss,  and  adhesive  properties 
into  consideration,  is  No.  4  containing  0.16  A1203. 

Series  V. 

VARIATION    OF    ANTIMONY    OXIDE. 

This  series  as  well  as  the  remaining  two  series  was  carried 
out  in  two  parts,  A  and  B,  the  two  parts  being  practically  alike 


REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS    F(  >K    CAST    [RON.    I  9 

-except  for  the  silica  content.  Part  B  was  carried  out  first  and  the 
limits  of  Sb203  were  not  high  enough,  hence  these  were  changed 
in  A. 

Series  V,  A. 

o.i6K,0     ] 

0.05  ZnO        0.16AUO3  ]   i.8Si02 

o.ioCaO      \ 

o.isPbO     |o.2oB,03    Jo-o.i4Sb203 

o .  54  Na20  J 


Series  V,  B. 


0 

I6K20    1 

0 

05  ZnO 

0 

10  CaO 

0 

15  PbO 

0 

54Na20  J 

0.16  A1,0, 
o .  20  B,0:f 


2.0  SiO, 

o  -o .  1  1  Sb20.., 


V,  A.     Batch  formulae  (in  equivalents). 


6 
S3 

O 

u 

•0 

a 
0 

pi 

C 

a 

N 

0 
to 

0 

"0 

u 

X 
rt 

a 

Borax 
K.  Spar 

s 

0 

W 

I 

2 

3 

4 

5 

6 

7 

8 

0-35 

0-35 

o-35 
o.35 
o.35 
0.35 
o-35 
0.35 

O.O5 

O.05 
0.05 
0.05 
O.05 
O.05 
0.05 
O.05 

0.05 

0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 
0. 10 

O.  IO 
O.  IO 
O.  IO 
O.  IO 
O.  IO 
O.  IO 
O.  IO 
O.  IO 

O.I3 

O.I3 
O.I3 
O.I3 
O.I3 
O.I3 
O.I3 
O.13 

1 .02 
I  .02 
1 .02 
1 .02 
1 .02 
1 .02 
1 .02 
1  .02 

O.OO 
0.02 
O.04 
O.06 
O.08 
O.  IO 

0.12 

0. 14 

V,  B.     Batch  formulae  (in  equivalents). 


0 

0 

0 

to 

1 

0.35 

2 

o-35 

3 

0-35 

4 

0.35 

5 

o-35 

6 

0.35 

<& 


N 


U 


a 


0.05 
0.05 
0.05 
0.05 
0.05 
0.05 


0.05 
0.05 
0.05 
0.05 
0.05 
0.05 


0.06 
0.06 
0.06 
0.06 
0.06 
0.06 


0.06 
0.06 
0.06 
0.06 
0.06 
0.06 


o.  10 

O.  IO 

O.  IO 

O.  IO 

O.  IO 

O.  IO 


O.  IO 
O.  IO 
O.  IO 
O.  IO 
O.  IO 
O.  IO 


0.13 
0.13 
0.13 
0.13 
0.13 
0.13 


0.00 

0.022 

0.044 

0.066 
0.088 

O.  I  I 


Description  of  Trials. — The  trials  of  enamel   1   A  have  but 


20      REPLACEMENT    OF   TIN    OXIDE    IN   ENAMELS   FOR   CAST   IRON. 

slight  opacity.  No.  2  A  has  a  trifle  more  and  so  on  up  the  series. 
Enamel  No.  3  A  has  a  fair  opacity,  No.  4  A  and  5  A  are  good 
enamels,  No.  5  A  being  the  whitest.  No.  6  A  is  a  good  enamel. 
It  is  whiter  than  No.  5  but  is  not  quite  so  glossy.  No.  7  is  a  good 
enamel  and  is  a  trifle  "matte"  in  texture.  No.  8  has  a  beautiful 
matte  texture  and  differs  from  all  the  rest  of  the  series  in  this 
respect.  One  of  the  trials,  however,  shows  a  tendency  to  shiver 
but  this  may  possibly  be  due  to  the  mode  of  application.  Enamel 
No.  5  is  the  best  of  the  A  part  of  the  series,  taking  gloss,  finish, 
and  general  appearance  into  consideration,  while  for  a  dull  or 
matte  texture  No.  8  is  the  best.  Enamels  No.  7  and  8  require 
a  higher  temperature  for  burning,  thus  indicating  that  high 
antimony  decreases  the  fusibility. 

With  part  B  of  the  series  shivering  is  more  evident  in  every 
case.  The  enamels  which  held  are,  however,  of  greater  brilliancy 
and  opacity,  enamel  No.  2  of  A  being  identical  in  appearance 
with  No.  1  of  B.  Enamels  2,  3  and  4  of  part  B  are  practically 
the  same  as  3,  4  and  5  of  part  A  respectively.  From  this  we  would 
conclude  that  0.016  equivalent  of  Sb203,  in  this  range  of  silica 
content,  has  about  the  same  opacifying  effect  as  0.02  equivalent 
of  silica. 

Series  VI. 

REPLACEMENT  OF  ANTIMONY  OXIDE  BY  TIN  OXIDE  IN  AN  ANTIMONY 

ENAMEL. 

This  series,  also  using  two  different  equivalents  of  silica, , 
was  carried  out  as  follows: 

VI,  A. 

0.16  K20     ] 

o.o5ZnO      I0.16AUO3    ]   i.8oSi02 


o.  10  CaO 

0.15  PbO      I  0.20  B.,03     J  0.075  Sb.5O3-o.15  SnO., 

o .  54  Na,0    J 


VI,   B. 

0.16  K20 

] 

0.05  ZnO 

|  0.16  A1,0.;   ]  2.0  Si02 

0.  10  CaO 

f                         r 

0.15  PbO 

1  0.20  B20,     J  0.075  Sb„03-o.i5  SnO. 

0 .  54  Na20 

J 

REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS   FOR    CAST    [RON.      21 


Hatch  formulae  (in  equivalents). 
VI,  A 


d 

-' 

3 

0 

N 

5 

c 
3 

M 

CO 

E 

: 

: 
c 

I.  .  .  . 

0.35 

0.05 

O.O5 

0.03 

O.O6 

O.IO 

O.IO 

0.13 

1.02 

0.075 

0.00 

j.  .  .  . 

035 

0.05 

O.O5 

0.03 

O.06 

O.IO 

O.IO 

0.13 

[.02 

0.056 

0.038 

3-  ■•  • 

0-35 

0.05 

O.O5 

0.03 

O.06 

O.IO 

O.IO 

0.13 

1.02 

0.038 

0.075 

4 

0.35 

0.05 

O.O5 

0.03 

O.06 

O.IO 

O.IO 

0.13 

I  .()_• 

0.019 

O.]  125 

5...  . 

0.35 

0.05 

O.O5 

0.0;, 

0.06 

O.IO 

O.IO 

0.13 

1.02 

0.00 

O.15 

VI,  B. 


I. ... . 

o.35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

[.22 

O.O75 

O.OO 

2.  .  .  . 

o.35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.22 

O.O56 

O.O38 

3 

o-35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

[.22 

O.O38 

O.O75 

.1 

o-35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.22 

O.OI9 

O.II25 

5 

o.35 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

[.22 

O.OO 

O.I5 

Description  of  Trials. — All  enamels  of  the  A  part  of  the  series 
adhere  tenaciously  and  are  good  enamels.  Enamel  No.  1  has 
more  opacity  and  whiteness  than  Xo.  5,  these  two  properties 
decreasing  uniformly  between  these  extremes.  The  antimony 
enamel  requires  a  slightly  higher  temperature  for  maturing,  but 
not  to  such  extent  as  to  be  detrimental  to  the  iron. 

In  the  B  part  of  the  series  shivering  is  much  in  evidence, 
due  to  the  increased  silica.  Enamels  Nos.  1  and  2  have  good 
opacity  but  Nos.  3  and  4  are  much  inferior  in  this  respect.  In 
enamel  No.  5  the  silica  has  dissolved  the  Sn02  almost  entirely. 
Taking  the  results  of  this  series  we  would  conclude  that  Si02 
at  the  higher  limit  is  opposite  in  effect  with  regard  to  SbaOa  and 
SnO,.  In  the  case  of  Sb,03  the  opacity,  whiteness  and  brilliancy 
are  increased,  while  with  Sn02  these  properties,  notably  the 
opacity,  are  decreased.  Shivering,  however,  is  increased  in 
either  case.  The  results  obtained  in  part  A  of  the  series  are  not 
in  accord  with  those  of  Riddle  whose  high  limit  of  silica  was  1.25 
equivalents.  In  enamel  No.  5  part  A  as  given  above,  a  good 
white  enamel  was  obtained  using  i.S  equivalents  of  silica. 

It  might  be  interesting  to  note  also  at  this  point,  the  be- 
havior of  the  enamels  on  wrought  iron.  The-  enamels  of  part 
A  were  applied  to  iron  washers,  and  although  they  had  not  been 


2  2       REPLACEMENT    OF   TIN    OXIDE    IN   ENAMELS   FOR   CAST    IRON. 

previously  cleaned,  the  enamels  held  perfectly  and  were  of  good 
whiteness,  brilliancy  and  texture. 

Series  VII. 

VARIATION    OF    BORIC    OXIDE. 

This  series  employs  two  equivalents  of  silica  and  the  Na2C03 
content  is  varied  in  order  to  reach  the  lower  limit  of  B203  still 
maintaining  the  same  ratio. 


VII,  A. 
0.16  K20     ] 
0.05  ZnO     J  0.16  A1203 
o.  10  CaO 
0.15  PbO 
o .  54  Na20 


o.  10-0.40  B203  J  0.075  Sb203 
VII,  B. 

]  2 .  00  SiO., 


0.16  K20 

0.05  ZnO     J  0.16  A1203 

o.  10  CaO      \ 

0.15  PbO     I  o .  10-0 . 40  B203   J  0.075  Sb203 

0.54  Na20   J 

VII,  A. 
Batch  formulae  (in  equivalents) 


0 
Z 

O 
0 

■a 

h-1 
pi 

O 

e 

K 

O 

u 

■3 

u 
O 

0 

U 

Borax 
K.  Spar 

ft          7; 

1 

0.4 

o-375 

0.350 

0-325 

0.300 

0-275 
0.25 

O.O5 

O.O5 
O.05 
O.O5 
O.05 
O.O5 
O.O5 

O.O5 

O.O5 
O.O5 
O.O5 
O.O5 
O.O5 
O.O5 

0.03 
0.03 
0.03 
0.03 
0.03 
0.03 
0.03 

0.06 
0.06 
0.06 
0.06 
0.06 
0.06 
0.06 

O.IO 
O.IO 
O.IO 
O.IO 
O.IO 
O.IO 
O.IO 

O.05 

O.075 

O.IO 

0.125 
0.150 
0.175 

0.2 

0.13 
0.13 
0.13 
0.13 
0.13 
0.13 
0.13 

1.02 
1.02 
1.02 
1.02 
1.02 
1.02 
1.02 

0.075 
0.075 
0.075 
0.075 
0.075 
0075 
0.075 

3 

4 

5 

6 

7 

VII,  B. 


0.4 

0.05 

0.05 

0.03. 

0.06 

O.IO 

0.05 

0.13 

1.22 

0.375 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.075 

0.13 

1.22 

0.350 

0.05 

0.05 

0.03 

0.06 

O.IO 

O.IO 

0.13 

1.22 

0.325 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.125 

0.13 

1.22 

0.300 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.150 

0.13 

1.22 

0.275 

0.05 

0.05 

0.03 

0.06 

O.IO 

0.175 

0.13 

1.22 

0.250 

0.05 

0.05  1  0.03 

0.06 

O.IO 

0.200 

0.13 

1.22 

0.075 
0.075 
0.075 
0.075 
0.075 
0.075 
0.075 


REPLACEMENT    OF   TIN    OXIDE    IN    BNAMBLS    POR    CAM     [RON.      23 

Description  of  Trials. — All  enamels  of  part  A  adhere  will 
and  are  good  white  enamels  up  to  No.  6.  Nos.  6  and  7  have  a 
yellowish  east  and  are  not  all  desirable  enamels.  Bubbling  is 
also  evident  in  the  enamels  of  higher  B,03  content.  Enamel  No. 
1  is  the  whitest  of  the  five  enamels. 

The  results  obtained  in  part  B  are  substantially  the  same  as 
those  of  part  A.  The  enamels  are  whiter,  however,  than  the  ones 
of  the  same  B203  content  and  the  yellowish  cast  of  enamels  6 
and  7  of  part  A  has  disappeared  in  the  corresponding  enamck  of 
part  B.  Shivering  is  present  to  quite  a  large  extent  in  part  B, 
due  to  the  high  silica.  As  in  part  A,  bubbling  is  prominent 
in  the  enamels  of  the  higher  B203  content.  The  difference  in 
whiteness  of  the  high  and  low  B,03  enamels  in  part  A  is  not  so 
pronounced  in  this  part  of  the  series.  Enamels  B  1  and  B  7 
have  very  little  difference  in  whiteness,  B  1  being  a  little  the 
whitest.  The  difference  in  maturing  temperature  is  however 
quite  large  and  the  tendency  to  bubbling  is  more  evident. 

The  results  indicate  that  the  lower  the  B203  the  better  and 
whiter  are  the  enamels.  The  limits  for  desirable  enamels  are 
about  0.15-0.30  B203. 

LIMITS  OF  THE  INGREDIENTS. 

The  limits  of  the  ingredients  and  their  effects  established 
by  this  work  are  as  follows: 

Si02:  The  effect  of  silica  is  to  increase  brilliancy,  white- 
ness, acid-resisting  properties  and  gloss.  If  increased  too  high, 
shivering  takes  place  and  the  maturing  temperature  is  too  high. 
The  limits  are  about  1. 65-1. 85  equivalents,  those  nearer  the 
higher  limit  being  the  preferable. 

A1203 :  Increased  A1,03  increases  the  temperature  for  matur- 
ing and  gives  whiter  enamels.  The  high  limit  is  around  0.1S 
equivalent.  The  low  limit  was  not  established  but  for  com- 
mercial enamels  is  probably  about  0.13  equivalent. 

Sb003:  The  effect  of  Sb203  is  to  increase  the  maturing  tem- 
perature, and  to  increase  the  whiteness  and  opacity  when  em- 
ployed between  the  limits  of  0.0-0.09  equivalent  Sb2Os.  If 
used  between  the  limits  of  0.1-0. 14  equivalent  the  enamels  are 
dull  at  the  lower  limits  and  matteness  increases  at  the  higher. 


24      REPLACEMENT    OF    TIX    OXIDE    IN    ENAMELS    FOR    CAST    IRON. 

At  the  high  limit,  0.14  equivalent,  shivering  is  likely   to   occur. 
For  brilliant  enamels  of  good  opacity  and  texture  the  limits 
are  0.06-0.09  equivalent,  about  0.075  being  preferable. 

SnO., :  No  variation  of  the  Sn02  content  was  made  but  a 
good  enamel  was  obtained  using  0.15  equivalent  of  Sn02. 

B„03:  The  effect  of  increased  B203  is  to  lower  the  maturing 
temperature,  to  increase  the  tendency  to  produce  bubbles,  to 
decrease  the  whiteness  when  used  above  a  certain  limit,  increase 
gloss,  and  to  increase  the  solubility  of  the  enamel.  The  limits 
are  about  0.15-0.3  equivalent,  those  nearer  the  lower  limit  being 
preferable. 

BaO:  The  effect  of  BaO  in  Sb203  enamels  is  to  produce  a 
"puckery"  or  matte  effect.  This  is  no  doubt  due  to  the  sulphur 
arising  from  the  Sb203  and  the  fuel  gases,  which  comes  in  contact 
with  the  barium  compounds. 

The  most  likely  enamel  taking  all  points  into  consideration 
is: 

o.i6K,0     ] 

0.05  ZnO     I  o.  16  A1.,03    J   1 .80  SiOa 

o .  10  CaO      \ 

0.15  PbO      j  0.20BA     J0.075Sb.P3 

o.54  NaX>   J 


DISCUSSION. 

Professor  Stale y:  Why  do  you  not  include  the  fluorine  in 
your  formula?  No  one  will  be  able  to  calculate  the  batch  from 
the  formula  unless  you  do  so.  Moreover,  it  makes  a  vast  differ- 
ence whether  an  enamel  contains  a  small  or  a  large  amount  of 
this  element. 

Mr.  Brown:  I  do  not  think  it  is  necessary.  I  introduced 
it  as  cryolite,  using  0.06  equivalent  of  cryolite  throughout. 

Professor  Staley:  Mr.  Brown,  I  just  want  to  ask  one  more 
question.  Did  you  get  an  absolutely  pure  white  enamel,  or  was 
it  of  a  greenish  or  bluish  tint?  There  have  been  many  attempts 
made  to  use  antimony  in  place  of  tin  oxide  in  cast  iron  enamels, 
but  it  has  never  given  a  satisfactory  white.  They  get  a  tint 
they  call  white,  but  it  is  not  a  commercial  white.  Do  you  have 
any  idea  of  how  to  avoid  getting  that  greenish,  bluish  white  so 
characteristic  of  antimonv  oxide? 


REPLACEMENT    OF    TIN    OXIDE    IN    I-NAMI-I.S    POR    CAST    [RON.      25 

Mr.  Brown:  I  did  not  carry  on  work  to  eliminate  the  cast 
you  speak  of.  The  cast  was  not  present  to  an  aggravated  extent 
that  I  could  see.  A  number  of  others  said  the  same  thing.  There 
is  a  slight  bluish  cast  or  tint  in  some  of  the  trials 

Professor  Sialey;  In  your  final  enamel  as  well  as  in  all  the 
others? 

Mr.  Brown:  It  was  not  so  pronounced  in  this  case,  but 
more  so  in  the  enamels  of  higher  silica  content. 

Mr.  Hurt:  I  noticed  in  speaking  of  the  enameled  iron 
industry  they  always  speak  of  dusting  the  enamel  on  and  I  would 
like  to  get  a  little  description  of  what  the  mechanical  process  is — 
of  what  is  involved  in  this  dusting  on  of  the  glaze. 

Professor  Staley:  In  a  paper  ("The  Manufacture  of  Enameled 
Iron  Sanitary  Ware,"  Trans.  A.  C.  S.,  Vol.  VIII,  p.  172)  I  pub- 
lished several  years  ago,  you  can  find  a  description  of  the  ordinary 
method  of  making  a  piece  of  enameled  cast  iron.  The  only 
difference  between  the  method  described  there  and  the  method 
used  at  present  is  the  use  of  a  mechanical  agitator. 

Mr.  Burt:     What  mesh  sieve  do  you  use? 

Professor  Staley:     The  sieve  is  a  fifty-  or  sixty-mesh  sieve. 

Mr.  Brown:  I  would  like  to  ask  Professor  Staley  what  his 
opinion  is  of  the  fluorine  in  a  fused  enamel — whether  it  is 
volatilized  or  whether  it  is  retained  in  the  enamel.  I  have  read 
of  several  instances  where  they  analyzed  for  fluorine  and  found 
it  in  the  enamels  in  small  quantities. 

Professor  Staley:  That  is  all  a  matter,  in  my  mind,  of  how- 
hard,  how  long,  and  how  hot  you  heat  the  enamel.  You  can 
volatilize  it  all,  01  you  can  have  the  larger  portion  of  it  stay  in. 
If  it  is  all  volatilized  you  have  no  opacifying  effect  from  the  use  of 
fluorides.  In  cast  iron  enamels  that  are  heated  or  fritted  in  the 
ordinary  length  of  time,  the  large  bulk  of  fluorine  stays  in. 

NOTE  PREPARED  AFTER  READING  THE  PAPER. 

Professor  Bleininger:  It  seems  to  me  that  Mr.  Brown  has 
solved  his  problem  satisfactorily.  He  has  accomplished  two 
things,  viz.,  the  production  of  a  white  enamel  which  compares 
favorably  with  the  best  tin  enamels,  in  the  opinion  of  impartial 
observers,  and  he  likewise  has  shown  clearly  the  kind  of  enamel 


26     REPLACEMENT    OF   TIN    OXIDE    IN    ENAMELS   FOR   CAST   IRON. 

required  for  the  use  of  antimony  as  an  opacifier,  which  differs 
somewhat  from  the  common  type. 

As  regards  the  poisonous  quality  of  antimony  compounds. 
Rickmann,  Sprechsaal,  XLV,  115-117,  says  that  during  an  ex- 
perience of  ten  years  the  use  of  metasodium  antimonate  has  not 
proven  injurious.  However,  he  points  out  that  the  antimony 
oxide  compounds  (tartar  emetic,  etc.)  are  poisonous.  For  cast 
iron  enamels,  therefore,  the  use  of  Na2Sb203  might  be  a  perfectly 
feasible  solution. 


UNIVERSITY  OF  ILLINOIS  BULLETIN 

ISSUED      WEEKLY 

Vol.  XI.  MAY   11.    1914.  No.  37 

[Entered  as  second-class   matter   December    11,   1912,  at  the  post  office   at 
Urbana,  Illinois,  under  the  Act  of  August  24,  1912.] 


BULLETIN  No.   19 

DEPARTMENT  OF   CERAMICS 

R.  T.  STULL,  Acting  Director 


INVESTIGATION  ON  IRON  ORE  CEMENTS 


BY 

ARTHUR  .E.  WILLIAMS 


PUBLISHED  BY  THE   UNIVERSITY  OF    ILLINOIS,  URBANA 


19  13-1914 


Authorised  Reprint  from  the  Copyrighted  Proceedings 
Volume  VIII,  1912. 

NATIONAL  ASSOCIATION  OF  CEMENT  USERS. 
Philadelphia,  Pens  \. 

IRON   ORE   CEMENT.* 

By  Arthur  E.  Williams,  f 

Iron  ore  cement  is  a  product  intended  to  be  used  in  sea  water 
work.  This  material  is  now  manufactured  in  Europe  under  the 
name  of  Erz  cement.  According  to  Mr.  William  Michaelis,  Jr., J 
•  the  process  of  manufacture  is  similar  to  that  of  Portland  cement 
except  that  limestone  and  iron  ore  are  used  in  place  of  limestone 
and  clay.  United  States  Consul  Thackara§  gives  a  description 
of  its  manufacture  as  follows:  Chalk,  flintstone,  and  finely  ground 
ferric  oxide  are  used.  The  flint  and  iron  are  ground  together, 
then  mixed  with  the  chalk  and  water  and  screened  through  a 
fine  sieve.  The  screened  product  is  clinkered  in  a  rotary  kiln 
and  then  ground.  An  average  composition  of  iron  ore  cement, 
given  by  Michaelis  is: 

CaO 63 . 5  per  cent  A1203 1 . 5  per  cent 

Si02 20.5        "  MgO 1.5        " 

Fe203 11.0        "  Alkali 1.0 

The  effect  of  sea  water  is  undoubtedly  two-fold.  In  the  first 
place  chemical  reaction  may  take  place  between  certain  con- 
stituents of  the  cement  and  the  salts  in  sea  water,  and,  on  the 
other  hand,  the  mechanical  action  of  the  waves  carrying  large 
amounts  of  sand,  freezing,  thawing,  and  the  varying  pressure 
of  the  water  due  to  tide  help  to  injure  the  cement  submerged  in 
sea  water.  This  work,  however,  will  be  confined  to  the  chemical 
action  of  sea  water,  for  the  mechanical  action  is  of  minor  import- 
ance unless  the  cement  is  weakened  by  chemical  changes. 

The  reactions  which  take  place  between  Portland  cement 
and  sea  water  are  said  to  be  of  three  distinct  kinds.  First,  the 
action  of  MgCl2  and  MgS04  in  sea  water  on  the  calcium  hydrate 
formed  during  the  hardening  process  of  the  cement,  forming 
Mg(OH)2,  CaCl2,  and  CaS04.      Second,  the  action  of    gypsum, 

*  Under  the  direction  of  Mr.  R.  T.  Stull. 

t  Urbana,  111.     A   Thesis    for    the  Bachelor  of  Science  Degree  in  Ceramics,  University  of 
Illinois  in  1910. 

X  Eng.  News,  Vol.  58,  pp.  645-646. 

{  United  States  Consular  Reports.  June,  190S. 

U) 


2  Williams  on  Iron  Ore  Cement. 

CaS04  formed  above,  upon  the  calcium  aluminates  forming 
calcium  sulpho  aluminate.  Third,  the  crystallization  of  the 
gypsum  and  calcium  sulpho  aluminate  giving  an  increase  in 
volume,  thus  causing  the  disintegration  of  the  mortar. 

That  free  lime  is  present  in  set  Portland  cements  is  well 
known.  Lamine*  found  32  per  cent  of  CaO  in  cement  sub- 
merged in  the  Black  Sea  15  years.  Every  analysis  of  a  cement 
exposed  to  sea  water  shows  a  high  percentage  of  MgO.  Vicatf 
in  1840  showed  this  fact  clearly,  a  cement,  which  was  submerged 
in  sea  water  for  6  months,  was  analyzed.  A  sample,  taken  from 
the  surface  exposed  to  the  sea,  showed  10.4  per  cent  MgO  and 
19.3  per  cent  CaO  while  the  interior,  which  was  not  impaired, 
showed  1.87  per  cent  MgO  and  31.33  per  cent  CaO. 

A.  Meyer  J  states  that  cement  loses  strength  in  sea  water. 
The  MgS04  acting  with  the  silicate  of  lime  forms  Mg(OH)2  and 
calcium  sulphate.  The  CaS04  reacts  with  the  calcium  aluminates 
(A1203,  x  CaO)  of  the  cement,  forming  Al(OH)3  +  3  Mg(OH), 
+  CaS04  +  CaCl2. 

Charles  J.  Potter§  says  that  MgS04  is  the  most  active  con- 
stituent in  sea  water  on  cement.  He  found  that  MgCl2  softens 
cement  but  causes  no  expansion.  Potter  says  that  it  is  now 
definitely  believed  that  magnesium  salts  act  on  the  feebly  com- 
bined lime  and  alumina  compounds  which  on  taking  up  water 
of  crystallization  cause  bursting  of  the  concrete.  He  mixed 
calcined  red  brick  clay  with  Portland  cement  clinker  in  propor- 
tions of  6  to  10.  From  this  mixture  briquettes  were  made  and 
placed,  together  with  Portland  cement  briquettes,  in  fresh  water, 
sea  water,  and  sea  water  to  which  10  per  cent  MgS04  was  added. 
Both  of  these  cements  gained  strength  in  fresh  water.  In  salt 
water,  the  Portland  cement  briquettes  began  to  fail  after  5  weeks 
and  were  disintegrated  after  5  years.  These  cements  showed 
blistering  after  one  year,  which  was  followed  by  expansion  and 
bursting.  The  red  cement  improved  continually  but  took  8 
weeks  to  obtain  the  maximum  strength  that  the  Portland  cement 
had  obtained  in  5  weeks.  In  the  10  per  cent  solution  of  MgS04, 
the  Portland  cement  tested  500  lb.  in  a  month  and  then  went 


*  he  Ciment,  1901,  pp.  111-691-81. 

t  Iron  Ore  Cement — The  P.  C.  Co.  of  Hemmoor,  Hamburg,  Germany. 

}  Chemisettes  Central  BUM,  Vol.  73.  p.  1368. 

§Jour.  Soc.  Chem.  Ind.,  Vol.  28. 


Williams  on  Iron  Ore  Cement.  3 

back  to  zero  in  1  year.  The  red  cement  began  at  250  lb.  and 
increased  continually  to  1015  lb.  in  8  years.  Mr.  Potter  says 
that  the  chemical  combination  of  CaO,  Si()2,  and  AU03  and 
water  is  feeble  and  that  probably  accounts  for  the  ability  of 
magnesium  in  sea  water  to  be  so  active. 

The  experiments  of  Dr.  Michaelis*  and  Le  Chatelierf  lead 
them  to  the  conclusion  that  Portland  cement  suffers  in  solutions 
containing  sulphuric  acid  salts,  which  applies  to  sea  water.  A 
double  salt  is  formed  composed  of  gypsum  and  calcium  aluminate. 
This  sulpho-aluminate,  A1203,  CaO  -+-  3CaS04,  is  said  to  crystal- 
lize with  30  molecules  of  water,  which  process  must  be  accom- 
panied by  considerable  expansion.  Le  Chatelier  says  that  "the 
main  cause  if  not  the  sole  cause,  of  the  injuries  which  cements 
suffer  under  the  action  of  sea  water  is  the  formation  of  calcium 
sulpho-aluminate. 

Rebuff  at  +  says  on  the  contrary  that  sulpho-aluminates 
cannot  exist  in  cements  in  sea  water  but  agrees  with  Michaelis 
and  Le  Chatelier  that  calcium  aluminates  are  the  parts  of  cement 
most  easily  acted  upon  by  salts  in  sea  water. 

It  has  been  shown  that  calcium  ferrates  are  formed  similarly 
to  the  calcium  aluminates  and  that  alumina  could  be  replace*  1 
by  ferric  oxide  in  Portland  cement.  Dr.  Michaelis  puts  this 
knowledge  into  use  with  the  idea  of  overcoming  the  disintegra- 
tion in  sea  water.  The  result  of  this  application  is  the  Iron  Ore 
cement  of  today. 

Dr.  Michaelis  and  the  Royal  Experiment  Station  of  Charlot- 
tenburg  have  tested  these  cements  in  comparison  with  Portland 
cements  in  a  very  thorough  manner.  Mr.  William  Michaelis§ 
says  in  a  paper  read  in  the  United  States  that  tests  of  Erz  cement 
and  Portland  cement  were  made  with  both  neat  and  3  to  1  mix- 
tures which  were  placed  in  fresh  water,  sea  water,  and  water 
containing  five  times  more  salt  that  sea  water.  In  sea  water, 
the  Krz  cement  developed  a  much  greater  strength  than  the 
Portland.  In  the  strong  salt  water,  the  strength  of  the  Portland 
cement  decreased  rapidly  while  the  Erz  cement  showed  a  steady 
gain.      Briquettes  were  made  of  Iron  Ore  and  Portland  cement 

*  Ton  Industrie,  1S96.  p.  838. 
tic  Ciment,  1901,  p.  31-32. 
t  Ton  Induatrii  Zeitung,  1901,  p.  272. 
§  Enu.  News,  Vol.  58,  pp.  645-646. 


4  Williams  on  Iron  Ore  Cement. 

which  were  placed  in  a  salt  solution  of  five  times  the  normal 
strength  of  sea  water  under  pressure  of  15  atmospheres  for  a 
few  days.  This  condition  destroyed  the  Portland  cement  bri- 
quettes entirely,  while  the  Iron  Ore  cement  increased  in  strength. 

The  Royal  Experiment  Station  conducted  similar  tests  to 
the  above  but  much  more  elaborate.  Two  Iron  Ore  and  three 
Portland  cements  were  made  into  prisms,  using  a  3  to  1  mixture 
of  standard  sand  and  cement.  These  prisms  were  placed  in 
sea  water  and  water  containing  five  times  the  percentage  of  salts 
in  ordinary  sea  water.  In  addition  to  this,  these  three  solutions 
were  allowed  to  act  upon  test  pieces  made  of  cement  mixed  with 
varied  amounts  of  gypsum.  All  the  Portland  cement  mortars 
disintegrated  in  the  three-  and  five-fold  salt  solutions;  all  the 
Iron  Ore  cement  mortars  remained  intact  and  sound. 

United  States  Consul  A.  W.  Thackara*  investigated  this 
cement  for  use  on  the  Panama  Canal.  The  result  of  his  investi- 
gations was  the  adoption  of  this  cement  for  concrete  work  exposed 
to  sea  water.  Another  point  in  favor  of  this  cement  is  the  property 
of  slower  setting.  The  cement  is  weaker  than  Portland  for  the 
first  week,  but  then  gradually  gains  strength  and  exceeds  that  of 
Portland. 

Publications  of  previous  experiments  do  not  show  definitely 
the  best  composition  for  cements  giving  the  greatest  protection 
against  sea  water.  With  this  idea  in  view,  the  following  investi- 
gations were  undertaken: 

The  outline  of  procedure  in  these  experiments  is  as  follows: 
Newberry's  cement  formula,  x  (3CaO,  Si02)  +  y(2CaO,  A1203), 
was  used  as  a  basis.  Assuming,  according  to  Newberry,  that 
Fe203  could  replace  A1?03  and  form  2CaO,  Fe203,  a  triaxial  dia- 
gram was  plotted  (Fig.  1),  the  three  members  stationed  at  the 
three  corners  being  3CaO,  Si02,  2CaO,  A1203  and  2CaO,  Fe203. 
By  blending  these  three  members,  cements  could  be  obtained 
containing  various  amounts  of  the  calcium  aluminate  and  the 
calcium  ferrate. 

The  batch  weights  of  these  three  members  were  calculated 
and  about  15  kg.  of  each  were  weighed  up,  using  practically 
chemically  pure  materials.  Whiting,  flint,  aluminium  hydrate, 
and  red  oxide  of  iron  were  the  only  ingredients.     These  batches 

*  United  States  Consular  and  Trade  Reports,  June,  190S. 


Williams  on  Iron  Ore  Cement.  5 

were  ground  in  a  ball  mill,  then  passed  through  a  200-mesh  sieve; 
thus  getting  thorough  mixing  and  a  finely  ground  batch.  The 
formulae  for  the  cements  made  are  given  in  Table  I. 

The  following  cements,  No.  19,  20,  21,  22,  23,  24,  25,  36, 
37,  38,  39,  40,  42,  48,  49,  50,  51,  52,  53,  54,  58,  59,  60,  61,  62, 
and  65  on  triaxial  diagram  were  then  weighed  up,  blunged  thor- 
oughly, and  partially  dried  by  pouring  the  slip  into  plaster  molds. 


^CaOj^AAOiJ 


o     e> 
o      ' 


/ 

r\ 

/ 

<* 

/io  ih 

v° 

<So 

4> 

3<JS 

>*0 

-fc 

/d 

/      z\ 

jr 

K° 

G°/ 

/7 

2&J 

3Z 

AiO 

•Sb/ff 

27 

/    sh 

44 

V     46\efl 

*h&    \ 

26 

iy 

43 

A/  ^AfiO 

Jh/t     /a/ 

ZS 

/      42 

41 

\/     SSj/  5Ai0 

V 

\      V 

* 

<h/3    W   A 

36 

4S, 

S*J     38/    t53\ofi 

/\      V\      */ 

' 

" 

A       7\       A       \ 

■&/2      28/       23/ 

57 

40 

JJ 

y      s\/     cW    (?AqO  > 

/\       */\        */\ 

' 

• 

* 

' 

\    7\    7\    /\ 

>//       2t/       22./      Ja. 

30 

J?i 

OS.          GtJ      6S/     6G\ 

FIG.    1. TRIAXIAL    DIAGRAM. 


The  cements  were  then  rolled  into  small  balls  about  the  size  of  a 
marble,  dried,  dehydrated  in  a  down  draft  kiln  to  about  800° 
C.  and  placed  in  fruit  jars  ready  for  burning. 

These  cements  were  burnt  in  a  magnesite  test  kiln,  designed 
by  Mr.  Stull  of  the  Ceramic  Department,  especially  for  burning 
experimental  cements.  The  construction  of  this  kiln  is  shown 
in  Fig.  2.     The  success  of  this  kiln  is  a  noteworthy  fact  as  test 


6  Williams  on  Iron  Ore  Cement. 

kilns  suitable  for  this  purpose,  heretofore,  have  not  been  very 
satisfactory  owing  to  lack  of  control,  unevenness  of  temperature 
in  the  clinkering  chamber.  Kerosene  oil  was  used  for  fuel  with 
an  air  pressure  of  about  50  lb. 

The  temperature  at  the  time  the  clinker  was  drawn  from 
the  kiln  was  determined  first  by  means  of  a  Wanner  pyrometer. 
This  was  given  up,  however,  as  the  rapid  rate  of  burning  required 
a  higher  temperature  than  the  true  temperature  of  clinker  forma- 
tion. 

Table  I. — Formulae  of  Cements  Made. 


No. 

Formulae. 

Molecular  Ratio 
Si02:A10+Fe20a 

19 

l(3Ca0,Si02)  4-.2(2CaO,Al203)  4-.7(2CaO,Fe203) 

0.11 

20 

.l(3Ca0,Si02)  4-  1  (2CaO,AkOs)  4-.8(2Ca0,Fe203) 

0.11 

21 

l(3CaO  Si02)  4-  9(2Ca0,Fe>03) 

0.11 

22 

2(3CaO,Si02)  +  .S(2Ca0,Fe203) 

0.25 

23 

.2(3CaO,Si02)4-.l(2CaO,Al203)4-.7(2CaO,Fe203) 

0.25 

24 

.2(3CaO,SiO»)4-.2(2CaO,Al203)4-.fi(2CaO,Fe203) 

0.25 

25 

2(3CaO,Si02)  4-.3(2CaO,AW>3)  +.5(2CaO,Fe2Os) 

0.25 

36 

3(3CaO,Si02)  4-.2(2CaO,Al203)  4-.5(2CaO,Fe2C3) 

0.43 

37 

.3(3CaO,SiOo)  4-.l(2CaO,Al-03)  +.6(2Ca0,Fe»03) 

0.43 

38 

,3(3CaO,SiOs)  +  .7(2CaO,Fe203) 

0.43 

39 

.4(3CaO,SiOj)  4-.6(2CaO,Fe203) 

0.66 

40 

.4(3CaO,Si02)  4-.l(2CaO,Al203)  4-.5(2Ca0.Fe203) 

0.66 

42 

.4(3Ca0.Si02)  +  .3(2CaO,Al203)  +.3(2Ca0,Fe'>03) 

0.66 

48 

5(3Ca0.Si02)  4-  3(2Ca0,Als0a)  4-.2(2CaO,Fe'>03) . . . 

1.00 

49 

.5(3Ca0,Si02)  +.2(2CaO,Al>03)  +.3(2CaO,Fe203) 

1.00 

50 

.5(3CaO,Si02)4-.l(2CaO,AM)3)  +.4(2CaO,Fe-03) 

1.00 

51 

.5(3Ca0,Si02)  +.5(2CaO,Fes03) 

1.00 

52 

.6(3CaO,Si02)  4-.4(2CaO,Fe»03) ...                       

1.50 

53 

.6(3CaO,SiO-)  +.l(2CaO,A1.03)  4-.3(2CaO,Fe2Os) 

1.50 

54 

.6(3CaO,Si02) +.2(2CaO,AM)3)  +.2i2CaO,Fe203) . . . 

1.50 

58 

.7(5CaO,Si02)  4-.2(2Ca0,AI-03)  +.K2CaO,Fe203) 

2.33 

59 

.7(3CaO,Si02)  4-.l(2CaO,Al2Os)  4-.2(2Ca0,Fe203) 

2.33 

60 

.7(3CaO,SiOs)  4-  3(2CaO.Fc-.03) . .  . 

2.33 

61 

8(3CaO,Si02)  4-  2(2CaO,Fe-03) 

4.00 

62 

.8(3CaO,Si02)  +.l(2CaO,Al->03)  4-.l(2CaO,Fe203) 

4.00 

65 

.9(3CaO,Si02)  4-.l(2Ca0,Fe2O3) 

9.00 

Almost  all  of  these  cements  were  fused  till  the  surface  was 
glassy  in  appearance  before  the  cement  seemed  well  clinkered 
and  crystals  appeared.  Cements  No.  54,  58,  62,  and  65  appeared 
like  a  Portland  clinker,  except  darker  in  color  and  were  not  fused 
or  slag-like  in  appearance. 

The  clinker  was  first  reduced  in  a  jaw  crusher  and  then 
ground  in  a  disc  mill;  a  screen  test  showed  24.2  per  cent  on  150 
mesh  screen;  12.3  per  cent  on  200  mesh  screen;  and  the  remainder, 
63.5  per  cent  passed  200  mesh.  These  cements  show  that  they 
are  approximately  of  the  same  degree  of  fineness  as  the  average 
Portlands.     After  the  samples  were  ground,  pats  were  made  from 


Williams  ox  Iron  Ore  Cement. 


si  y  ii 


r~T~i 


: 

i  -*- 

L 

fl    > 

« 

1 

\ 

fxr 

FT-n 


! '  '*—  i 


®!t 


5  5 


'l         I 


s 


Williams  on  Iron  Ore  Cement. 


them  in  the  usual  manner  to  determine  the  properties  of  the 
cement. 

The  amount  of  water  used  for  mortar  was  determined  by  the 
Boulonge  method  (Waterbury's  Cement  Manual,  p.  44).  The 
initial  and  final  sets  were  determined  with  Gilmore  needles. 

Four  pats  were  made  of  each  cement  with  the  idea  of  using 
one  for  the  time  of  setting  tests  and  placing  the  other  three  imme- 
diately in  the  moist  closet,  two  of  which  were  to  be  used  for  the 
boiling  test  after  24  hours,  the  third  to  be  allowed  to  stand  in 


Table  II. — Results  of  Tests  on  Cements. 


Time  of 

Time  of 

Water 

Remarks 

Conditions 

No. 

Initial    Set, 

Final  Set, 

Used, 

at  Time  of 

after  4S  Hours 

hours. 

hours. 

per  cent. 

Final  Set. 

in  Moist  Closet. 

19 

IX 

3 

21.0 

Cracked  in  X  hour 

Cracked 

20 

1 

5 

20.0 

O.  K.  Strong 

Warped  and  cracked 

21 

2X 

5X 

21.0 

No  cracks 

No  cracks 

22 

IH 

4 

20.0 

Small  cracks 

No  cracks 

23 

i 

21.0 

Cracked 

No  cracks 

24 

% 

"hX 

22.0 

Cracked 

No  cracks 

25 

IX 

21.5 

Cracked 

No  cracks.     Soft 

36 

i% 

ii 

20.0 

Cracked 

O.  K. 

37 

i 

2X 

20.0 

Cracked 

No  cracks 

38 

i 

5 

20.0 

0.  K. 

No  cracks 

39 

2 

8 

21.0 

Cracked 

Cracked 

40 

IX 

3X 

20.0 

Cracked 

Warped 

42 

X 

2% 

21.5 

O.  K. 

No  cracks 

48 

1M 

7 

22.0 

O.  K. 

No  cracks 

49 

IX 

3 

21.0 

Cracked 

Cracked 

50 

3 

22.0 

Cracked 

No  cracks.     Soft 

51 

2 

io 

21.0 

O.  K. 

Soft 

52 

1 

9 

20.0 

Soft 

Soft 

53 

\x 

4 

21.0 

Cracked 

No  cracks.     O.  K. 

54 

1 

iX 

23.5 

Cracked 

No  cracks.     O.  K. 

58 

1 

3X 

22.0 

No  cracks 

Cracked 

59 

X 

4X 

21.0 

O.  K. 

Warped 

60 

IX 

5 

21.0 

Soft  and  crumbly 

Warped  and  cracked 

61 

1 

6 

22.0 

Warped 

O.  K. 

62 

IX 

22.0 

Did  not  harden 

O.  K. 

65 

IX 

21.0 

Cracked 

Warped 

water  for  28  days.  All  of  these  cements  went  to  pieces  in  cold 
water  or  in  the  boiling  test.  The  results  are  given  in  Table  II. 
From  these  cements,  one  only,  i.  e.,  No.  62,  remained  sound 
when  placed  in  water.  This  cement  also  stood  the  boiling  test 
(|  hr.),  the  others  going  to  pieces.  The  molecular  ratio  of  Si02 
to  AI2O3  for  this  cement  is  four  and  since  the  molecular  ratio  for 
good  cements  is  between  5.1  and  6.8  and  since  none  of  these 
cements  lie  between  these  limits,  it  was  decided  to  construct  a 
new  group.  Cement  No.  62  approached  these  ratios  nearer  than 
any  other. 


Williams  on  Iron  Ore  Cement.  9 

A  new  hatch  was  calculated  after  Bleininger's  formula 
(2.8CaO,Si02)  +  (2CaO,  A1,03)  having  different  amounts  of 
Fe203  and  AhO:,  and  also  the  ratio  of  SiOa  to  AhO;i  -+■  Fe203 
varied  from  just  above  to  just  below  the  limits.  The  using  of 
chemically  pure  raw  materials  in  place  of  slag  and  limestone 
gives  less  efficient  mixtures  of  lime  and  Si02.  It  was,  therefore, 
thought  that  sufficient  lime  would  he  obtained  by  the  use  of 
Bleininger's  formula.     For  formula1  see  Table  III. 

Table  III. — Formcl.e  fob  Cements  Made. 


No. 


Formulae. 


-4i 
At 
A3 
A, 
B, 
B2 
B3 
B4 
Ci 
Ci 
C3 
d 


5.1(2.8CaO,Si02)+(2Ca  ,Fe03) 
.VN(2,SCa<  ».Si<>.)  4-(2CuO.Fi->03) 
6.4(2.8<  !a<  ),Si(  h)  4-(2CaO,FesOs) 
".(l(2.sCaO.Si02)+(2Ca(),Fc203) 

5  2S  2  8CaO.SiOs) +0.175(2CaO,AbOa) +.825(2CaO,Fe20s) 
(i.0()(2.sCa(  >,Si(  >»)  +.l75(2Ca<  ),AUOj)  +.825(2CaO,Fe20a) 
6.40(2.8CaO,SiO2)  H-.200(2CaO,AliO8) +.800(2CaO,Fe2O3) 
7.22(2.8CaO,Si02)  +.175<2CaO,Ab(  >s)  +.825(2Ca<  >,Fe203) 
5.44(2. SCaO,Si02)  +.360(2CaO,Al,.<  >j)  +.640(2Ca(  ),Fe203) 
5.80(2.8CaO,S1Os)+.400(2CaO,Al2Os(+.600(2BaO,Fe2O3) 
6.40(2.8CaO,SiO2)  +.400(2CaO,Al2O3)  4-.«00(2CaO,Fe2O3) 
7.00(2.SCaO,SiO2)  +.400(2CaO,Al2O3)  +.600(2CaO,Fe2O3) 


Percentage  Composition. 


Molecular 

No. 

CaO 

AhOs 

Fe203 

Si02 

Ratio 
R203:Si02 

-4i 

66.0 

0.0 

11.6 

22.4 

5.1 

At 

66.7 

0.0 

10.4 

22.9 

5.8 

-43 

67.2 

0.0 

9.6 

23 . 2 

ti.4 

A, 

67.5 

0.0 

8.9 

23.6 

7.0 

Bi 

66.7 

1.3 

9.4 

22.6 

5.25 

B2 

67.4 

1.1 

8.4 

23.1 

6.00 

Bz 

67.5 

1.3 

7.8 

23.4 

6    Hi 

B, 

68.1 

0.9 

7.2 

23.8 

7.22 

Ci 

07.4 

2.5 

7.2 

22.9 

5.44 

C2 

68  0 

2.7 

6.0 

23.3 

5.80 

C3 

68.2 

2.5 

5.8 

23 . 5 

6.40 

d 

l,S    .", 

2.3 

5.4 

23.8 

7.00 

These  cements  were  prepared  in  the  same  manner  except 
that  the  temperature  of  clinkering  was  determined  as  near  as 
possible  by  the  method  used.  The  kiln  was  allowed  to  cool  to 
about  1000  deg.  C.  before  a  hatch  of  cement  was  put  in  and  tem- 
perature was  then  gradually  raised  till  clinker  was  formed,  the 
temperature  was  then  read  with  a  Wanner  pyrometer. 

The  clinkers  obtained  appeared  exceptionally  good,  being 
dull  black  in  color  and  glistening  brightly   in  the  sun.      These 


10 


Williams  on  Iron  Ore  Cement. 


clinkers  were  pulverized  the  same  as  has  been  previously  de- 
scribed, then  tested. 

The  results  of  these  tests,  Table  IV,  show  that  good  cements 
can  be  obtained  with  a  large  amount  of  alumina  using  the  same 
ratio  of  Si02  to  R203  as  Portland  cements  require.  One  very 
noticeable  fact,  however,  is  that  when  no  A1203  is  present  as  in 
series  A,  A-2,  A3,  and  A4  these  cements  all  show  expansion,  thus 
giving  evidence  of  free  lime.  Although  A\  stood  the  boiling  test, 
the  cubes  made  from  this  cement  bulged  out  from  the  mold 
considerably. 

The  question  arises  at  this  point,  is  it  always  necessary  for 
AI0O3  to  be  present  or  can  a  good  cement  be  made  without  it? 


Table  IV. — Results  of  Test. 


Temperature 

Time  to 

Clinker, 

hours. 

when 

Appearance 

Initial    Set, 

Final  Set, 

H2O, 

No. 

Clinkered, 
deg.  C. 

of  Clinker. 

hours. 

hours. 

per  cent. 

A\ 

1300 

X 

24 

62 

24.8 

Ai 

1320 

V2 

All 

22 

56 

24.0 

-43 

1320 

llA 

clinkered 

26 

56 

23.2 

Ai 

1330 

V2 

good, 

2S 

60 

26.0 

Bi 

1390 

V2 

colored  black 

4% 

40 

26.3 

£2 

1320 

IX 

and 

4^ 

44 

24.4 

B3 

1350 

X 

glistening 

11 

36 

28.0 

Bt 

1400 

IV* 

with 

5 

4S 

25.0 

Ci 

1320 

Wi 

crystals 

5 

30 

24.4 

Ct 

1320 

X 

in  a 

12 

40 

24.0 

C3 

1330 

ix 

bright 

12 

48 

28.0 

d 

1380 

y2 

light 

17 

40 

27.2 

This  ought  to  be  possible  by  reducing  the  lime  content,  as  Ai 
was  the  best  of  series  A  and  also  had  the  smallest  amount  of 
lime  silicate. 

The  slowness  of  setting  is  another  factor  which  must  be 
considered.  It  will  be  seen  by  Table  IV  that  all  of  the  cements 
required  a  long  time  to  harden.  This  must  be  carried  on  in  a 
moist  atmosphere  also  or  the  cement  will  dry  out  before  it  has 
completely  hydrated  and  set.  The  above  factors  will  perhaps 
limit  the  use  of  this  cement  to  work  under  water  which  may  be 
allowed  to  set  a  considerable  time. 

All  the  cements  of  series  B  stood  a  6-hr.  boiling  test  with- 
out showing  any  signs  of  expansion.  In  series  C  all  but  G  stood 
the  boiling  test.     &  warped  a  little  and  came  loose  from  the  glass 


Williams  on  Iron  Ore  Cement. 


11 


plate  although  the  cement  has  a  comparatively  low  lime  content 
and  its  formula  lies  between  other  good  cements. 

The  attempt  was  next  made  to  give  these  cements  a  com- 
parative test  with  Portland  cement  to  show  their  relative  resist- 
ance to  sea  water.  The  method  used  was  similar  to  that  of  Dr. 
Michaelis. 

One-inch  cubes  were  made  of  each  series  of  cements  together 


FIG.   3. — STEAM    CYLINDER. 


with  a  set  of  cubes  of  a  standard  commercial  Portland  cement, 
which  had  stood  all  the  commercial  tests.  These  were  allowed 
to  stand  60  hr.  in  the  moist  chamber  and  then  placed  in  water, 
remaining  in  water  for  27  days.  The  cubes  made  from  series  A 
together  with  a  set  of  5  Portland  cement  cubes  were  placed  in  a 
steam  cylinder,  Fig.  3,  containing  an  artificial  sea  water  solution 
of  ten  times  normal  strength.  The  quantity  of  salt  is  shown  in 
Table  V.      The    cements    were    then    put    under   steam   pressure 


12 


Williams  ox  Iron  Ore  Cement. 


of  125  lb.  or  8|  atmospheres,  the  temperature  being  between 
150  and  200  (leg.  C.  This  was  continued  for  3  days.  On  opening 
the  cylinder,  the  salt  solution  was  found  to  be  very  dilute  due 
to  condensation  of  steam  and  no  visible  action  on  the  cements 
had  occurred.  The  salt  solution  and  cubes  were  then  put  into 
a  large  wide-mouthed  bottle,  provided  with  a  stopper  and  small 
vent  hole.  The  bottle  was  then  placed  inside  the  pressure 
cylinder  and  steam  admitted,  allowing  little  or  no  condensation. 
After  being  sure  that  the  bottle  was  not  broken  by  the  first  change 
in  temperature,  the  pressure  was  kept  on  for  3  days  longer. 
Upon  opening  the  cylinder,  the  cubes  were  found  bone  dry  and 
covered  with  salt  and  the  bottle  cracked.  This  was  due,  no 
doubt,  to  the  rapid  reduction  of  the  pressure,  allowing  the  water 


Table  V. — Analysis  of  Sea  Water.* 


37.3  parts  per  thousand  parts  water. 
100  parts  =2700  parts  water. 
12000 


2700 


Salt. 

Per  cent  of  Salt.             Ten  tin?es  per  cent 
of  Salt. 

Total  for  12  liters 
of  Water. 

NaCI 

MgCb 

MgS04 

CaSOi 

K^SOj 

77.75 

10.87 
4.73 
3.60 
2.46 

10S.7 
47.3 
36.0 

342.10 
478.28 
208.12 
158.40 
10.80 

MgBr 

CaHC03 

0.217 
0 .  34.5 

0.93 
1.62 

=  4.4  factor  times  per  cent  of  salt  =quantity  per  12  liters  of  water. 


to  vaporize  rapidly,  which  was  at  a  temperature  above  its  boiling 
point. 

The  results  of  this  test  were  contrary  to  what  was  expected 
as  the  Portland  cements  were  untouched  and  all  of  the  iron 
cements  were  cracked  and  swollen.  This  cracking  and  swelling 
is  caused,  no  doubt,  by  an  excess  of  free  lime,  as  these  cements 
showed  an  expansion  in  the  boiling  test  and  there  was  a  deposit 
of  hydrated  lime  in  the  bottom  of  the  cylinder  which  seemed  to 
have  been  leached  out  of  the  cubes. 

No  crushing  strength  test  of  Series  A  was  made  as  they 
were  all  destroyed  already. 

Series  B  was  then  placed  in  the  cylinder,  with  a  set  of  Port- 


*  University  Geological  Survey  of  Kansas,  Vol.  7,  p.  27. 


Williams  on  Iron  Ore  Cement. 


13 


land  cement  cubes.  A  vessel  made  of  4-in.  pipe  was  used  in 
place  of  the  glass  bottle  to  overcome  cracking  due  to  sudden 
change  in  temperature.  This  series  was  kepi  under  pressure  for 
6  days,  and  when  removed  from  the  cylinder  neither  the  Portland 
or  Iron  Ore  cements  appeared  harmed  except  cement  B3  which 
went  to  pieces.  The  reason  for  the  disintegration  of  this  cement 
is  unexplainable  except  that  it  was  not  clinkered  properly.  The 
boiling  test,  however,  showed  a  good  cement.     (Table  VI.) 

As  the  crushing  strength  tests  of  the  Portlands  show,  there 
seemed  to  be  no  weakening  due  to  being  in  the  salt  solution. 


Table  VI. — Results  of  Boiling  Test  for  6  Hours,  after  60  Hours  in 

Moist  Chamber. 


Number. 

Appearance  after 
Sea  Water  Test. 

Ai 

Good, 
cracked  plate. 
Came  loose  from  plate  and  showed 
some  expansion. 

Same  asA3. 
Good. 

Came  loose  from  plate,  warped. 
Good. 
Good. 

At... 

A, | 

I 

Bi 

Bi 

£3 

b\ ::::.. 

Ci 

Ci 

C3 

Ct 

Also  the  strength  of  the  Portlands  seems  to  average  higher  than 
the  Iron  Ore  cements.     (Table  VII.) 

Five  cubes  of  each  cement  of  Series  C  were  then  placed  into 
the  cylinder  with  a  set  of  Portland  cubes  made  at  the  same  time. 
These  were  kept  under  pressure  for  8  days.  The  results  of  this 
series  were  quite  different  as  4  of  the  5  cement  cubes  were  badly 
cracked  and  had  begun  to  swell.  C2,  C3,  and  C4  showed  no  signs 
of  disintegration,  but  C\  was  cracked  and  swollen  badly.  This 
cement,  as  the  A  Series,  did  not  stand  the  boiling  test  and  such 
an  action  would  be  expected  from  it  under  the  extreme  condi- 
tions in  the  pressure  cylinder.  The  crushing  strengths  of  C2, 
C3,  and  C4  averaged  lower  than  the  B  Series,  C2  was  so  soft  that 
disintegration  had  evidently  set  in. 


14 


Williams  on  Iron  Ore  Cement. 


Table  VII. — Crushing  Strength  of  Cements. 


Pi 


B2 


C2 


Cz 


Ct 


No. 

Cross-sectional 
Area,  sq.  in. 

Crushing  Strength. 

Average, 
lb.  per  sq.  in. 

Total  lb.                   Lb.  per  sq.  in. 

Pi 

Pi  =  Portlands  in  fresh  water  3  weeks. 
1.08                               7680                              7100 
0.975                            4780                              4900 
1.06                               6650                              6280 
1.045                             5650                               1910 
1 .  105                             7750                              7020 

6042 

p2  =  Portland  cement  in  fresh  water  4  weeks. 
0.97  7850  8700 

0.95  6620  6970 

0.97  7730  7960 

P=  pressure  with  Series  B  of  the  Iron  Ore  Cements. 


7876 


0.97 

1.25 

1.025 

0.98 

1.01 


5420 
4860 
7650 
7330 
7200 


3890* 
7470 
7470 
7150 


6920 


Iron  Ore  Cement  in  salt  solution  under  pressure  cylinder  6  days. 

5620 
6250 
4915 
4460 
4860 

6500 
6000 
7100 
7550 
5930 

4120 
4820 
4540 
6240 
5350 

4080 
4360 
6660 
5310 
4660 

2190 
1660 
2400 

1SSO 
24  SO 

3000 
6150* 

3331 1 
4SO0 
3900 

Portlands  in  Cylinder  7  days  with  Series  C. 


1.035 

5810 

1 .  075 

6720 

1.035 

5120 

1.06 

4740 

1.045 

5200 

1.105 

7170 

1.02 

6620 

1.055 

7500 

1.115 

8430 

1.125 

6680 

1.09 

4480 

1.075 

5180 

1.10 

5000 

1.06 

6610 

1.12 

6000 

1 .  025 

4200 

1.03 

5400 

1.025 

6320 

1.1 

5850 

1   04 

4850 

1.05 

2280 

0.97 

1580 

1.1 

2640 

1.00 

1820 

1.01 

2500 

1.07 

5220 

1.07 

6630 

1 .  06 

3630 

1.07 

r,l  to 

1.04 

4  ().-)() 

5241 


6616 


5014 


4914 


2110 


5757 


0.99 
0.97 


3000 
6720 


3030 

6930* 

Only  unaffected 

Portland  cement 

cube. 


*  Signifies  not  calculated  in  average. 


Williams  on  Iron  Ore  Cement.  15 

Conclusions. 

As  the  time  for  this  investigation  was  limited,  further  work 
could  not  be  done,  and  the  conclusions  which  may  be  drawn 
from  these  results  are  limited.     This  much  may  be  said,  however: 

1.  The  amount  of  lime  or  silicate  of  lime  ought  to  be  less 
when  Fe203  alone  is  used  in  place  of  AI2O3,  as  the  lowest  ratio 
of  Series  A  5.1  was  the  only  one  which  stood  the  boiling  test. 
Scries  B  showed  that  the  limits  gave  good  cements  throughout, 
neglecting  B3  which  must  have  disintegrated  due  to  some  other 
cause.  Series  ('  showed  that  the  lime  and  silica  required  increased 
as  the  lower  ratio  5.44  disintegrated  and  the  higher  ratios  were 
good.  To  sum  this  up,  when  all  iron  is  used  the  R203  :  Si02 
ratio  should  be  below  5.1;  when  0.175  to  0.2  mols.  A1203  is  used 
with  0.825  to  0.8  mols.  of  Fe203  the  ratios  lie  between  5.1  to 
7.22.  If  0.36  to  0.4  mols.  of  A1,03  the  ratio  must  be  5.8  or  greater. 
This  is  but  a  suggestion  and  will  require  further  experimenting 
to  show  it  definitely. 

2.  That  cements  with  large  amounts  of  Fe203  will  stand  saline 
solutions  better  than  cements  containing  A1203  was  shown  in 
the  test  of  Series  C  where  the  Portlands  were  actually  disinte- 
grated and  the  iron  cements  stood  the  same  test. 

3.  The  results  seem  to  suggest  that  if  the  amount  of  lime  was 
reduced  lower  than  2.8  CaO  in  Bleininger's  formula,  better  strength 
could  be  obtained.  There  was  found  in  the  bottom  of  the  vessel, 
after  each  trial  in  the  cylinder,  a  heavy  muddy  deposit  which 
was  principally  hydrated  lime  and  which  appeared  to  have  been 
Leached  from  the  cubes.  This  reduction  of  the  amount  of  lime 
may  not  need  to  be  as  much  as  the  results  suggest  if  the  raw 
materials  were  clay  and  limestone  in  place  of  pure  whiting, 
AloCOH),;  and  flint.  All  of  the  iron  cements  would  have  stood 
the  tests  better  if  they  had  been  allowed  to  stand  in  the  atmosphere 
and  age,  thus  giving  the  lime  time  to  become  calcium  carbonate. 
The  Portland  cement,  which  these  cements  were  tested  against, 
was  one  of  the  best  cements  on  the  market.  It  tested  as  follows: 
Initial  set,  3  hr.;  final  set  4  5  hr. ;  tensile  strength  of  neat  cement 
after  seven  days,  (57!)  lb.:  after  28  days,  774  lb.;  and  its  crushing 
strength  is  shown  in  the  tables.  This  cement  had  also  aged 
several  months  in  the  Laboratory  and  was  in  the  best  of  condition 


16  Williams  on  Iron  Ore  Cement. 

to  stand  accelerated  tests.  The  percent  of  lime  given  by  Mr. 
William  Michaelis  is  63.5  per  cent  with  a  small  amount  of  magnesia, 
MgO,  1.5  per  cent.  The  cements  made  for  this  thesis  are  all 
above  66  per  cent,  this  is  only  another  evidence  that  these  con- 
clusions are  correct  and  the  following  formula  is  suggested  as  the 
center  of  a  series  of  cements  for  further  experimenting: 

4(2.8  CaO,Si02)  0.8  (2  CaO,  Fe203)  0.2  (2  CaO,  A1203). 

from  this  vary  both  the  amount  of  Si02  and  CaO. 

Bibliography. 

William  Michaelis,  Jr.,  Engineering  News,  Vol.  58,  pp.  645-646. 

Charles  J.  Potter,  Journal  Society  Chemical  Industry,  Vol.  28. 

Newberry,  Journal  Society  Chemical  Industry,  Vol.  16,  No.  11. 

A.  Meyer,  Chemisches  Central  Blatt,  Vol.  73,  p.  1369. 

A.  Spencer  and  E.  C.  Eckel,  Patent  No.  912,266,  U.  S. 

Karl  Zulkowski,  Chemische  Industrie,  1901. 

A.  W.  Thackara,  U.  S.  Consular  Reports,  June,  1908. 

Iron  Ore  Cement,  The  P.  C.  Co.  of  Hemmoor,  Hamburg,  Germany. 

Lamine,  Le  Ciment,  1901,  pp.  Ill,  691,  81. 

Dr.  Michaelis,  Tone  Industrie  Zeitung,  1896,  p.  838. 

Rebuffat,  Tone  Industrie  Zeitung,  1901,  p.  272. 

Le  Chatelier,  Le  Ciment,  1901,  pp.  31-32. 


£n  JUN  3  °  1915 


UNIVERSITY  OF  ILLINOIS  BULLETIN 

ISSUED     WEEKLY 

Vol.  XL  JUNE  29,   1914.  No.  44 

[Filtered    as    second-class    matter    December    11,    1912,    at    the    post    office    at 
Urbana,    Illinois,    under  the   Act  of  August  24,    1912.] 


BULLETIN  No.  20 
DEPARTMENT  OE  CERAMICS 

R.   T.   STULL,   Acting  Director 


DESIGNS   OF   SEVEN   TEST   KILNS 

BY 
R.   T.   STULL  andR.    K.    HURSH 


PUBLISHED   BY  THE  UNIVERSITY  OF  ILLINOIS,    URBANA 


19  13-1914 


DESIGNS  OF  SEVEN  TEST  KILNS 

BY  K.    T.   STILL   AND   K.    K.    UIKSII,    1KUAXA,  ILLINOIS 

Iii  presenting  the  designs  of  these  test  kirns,  no  claims  are 
made  to  original  ideas.  In  the  design  of  each  kiln,  an  attempt 
has  been  made  to  combine  well-known  principles  in  such  a  man- 
ner as  to  best  meet  the  conditions  and  requirements  which  the 
kiln  is  to  meet. 

All  flues  leading  from  the  kilns  are  placed  under  the  floor. 
These  connect  with  two  main  tines  15  in.  wide  by  30  in.  deep, 
which  in  turn  connect  with  a  60  ft.  stack.  Kiln  represented  by 
Figs.  1  and  2  is  of  the  down-draft,  open  fire  type,  provided  with 
two  fire  boxes.  The  fire  boxes  are  short  and  wide,  facilitating 
easy  cleaning  and  prolonged  life  of  grate  bars.  The  kiln  is 
provided  with  a  flue  system  so  that  forced  draft  may  be  applied 
either  above  or  below  the  grates.  The  kiln  has  been  in  use  over 
two  years  and  has  been  fired  repeatedly  to  cone  16.  It  has  a 
surplus  of  draft  so  that  it  has  not  been  necessary  to  use  forced 
draft  to  reach  high  temperatures. 

In  Figs.  3  and  4  is  shown  a  recta  nglar  down-draft  muffle 
kiln.  The  muffle  is  2  ft.  by  3  ft.  and  3  ft.  to  the  spring.  The 
muffle  walls  are  laid  with  hollow  blocks  beveled  at  the  corners 
in  order  to  give  greater  radiation  surface.  The  same  size  and 
style  of  fire  box  is  used  in  this  kiln  as  in  the  former  one.  The 
kiln  has  been  burned  to  cone  8  in  twelve  hours.  After  two  years 
of  use.  it  is  in  excellent  condition. 

Figures  5  and  (i  represent  a  round  down-draft  open  fire 
kiln.  Fuel  oil,  delivered  to  the  kiln  under  5  lb®,  pressure,  and 
air  at  2  lbs.  are  used  in  firing.  The  four  burners  lead  tangen- 
tially  into  a  combustion  ring.  The  fire  gases  pass  up  over  a  cir- 
cular Hash  wall  and  down  through  the  perforated  floor. 

The  crown  is  removable  and  is  raised  and  lowered  by  a  three 
ton  chain  hoist  running  on  a  track.  This  arrangement  permits 
of  easy  and  quick  setting  and  eliminates  the  troublesome  cold 
doorway.  The  temperature  and  kiln  atmosphere  can  be  gov- 
erned very  closely.     The  kiln  has  been  in   use   for  more  than  a 


DKSKiXS    OF    SEVEN    TEST    KILNS 


DESIGNS  OF  SEVEN   TEST    KILNS  5 

year.  Although  it  is  capable  of  attaining  very  high  tempera- 
tures, there  has  beeD  no  occasion  to  fire  it  above  cone  8.  This 
temperature  has  been  attained  with  only  two  burners  in  use. 

Figures  7  and  8:     Open   fire,  dowu-drafl    kiln:     The  kiln 
is  fired  by  gas  and  compressed  air,  both  being  preheated  in  coils 


of  wrought  iron  pipe  suspended  in  the  out-going  flue.  The  flue 
is  provided  with  an  opening  just  below  the  damper.  Through 
this,  air  can  be  admitted  in  order  to  prevent  over-heating  of  the 
coils.  The  kiln  is  hi-ed  by  ten  burners  made  from  ordinary  pipe 
fittings.  Each  burner  is  about  the  size  of  an  ordinary  Bunsen 
blast  lamp.    The  kiln  has  been  fired  to  eone  14  in  six  hours. 


DKSKiXS    OF    SEVEN    TEST    KILNS 


DESIGNS   OF   SEVEN    TEST    KILNS 


The  setting  chamber  i.>  12  in.  by  22  in.  by  9  in.  to  the 
spring,  and  -4  in.  rive.  The  kiln  is  especially  adapted  to  clay 
testjng.  Two  pings  in  tin-  crown,  ape  in  the  hack  and  one  in  the 
wicket,  are  provided  for  drawing  trials, 


Fig.    i 


Figure  9:  Battery  of  three  calcining  kilns:  Kadi  unit  is 
fired  by  fuel  oil  and  compressed  air.  The  combustion  chamber 
at  the  top  is  cylindrical  in  form,  the  Same  entering  tangentially. 
Each  unit  is  provided  with  two  calcining  chambers.  The  kilns 
are  designed  especially  for  burning  small  batches  of  Portland 
cement,  and  for  calcining  clays  and   dry  colors.     The   material 


8  DESIGNS  OF  SEVEN   TEST   KILNS 

to  be  calcined  may  be  placed  on  the  bottom  plate  of  the  chamber 
or  in  covered  flat  tile  saggers. 

Figure  10 :  Twin  muffle  kiln :  The  kiln  was  designed  es- 
pecially for  firing  enamels  for  metals  and  overglaze  colore.  Each 
muffle  is  heated  by  two  gas  burners,  the  air  being  preheated  in 
the  recuperator  below  the  muffle.  The  gas  passes  in  horizontally 
and  meets  the  air  coming  up  from  the  recuperator.  The  flame 
passes  back  to  the  opposite  end  of  the  muffle  then  turns  and 
passes  twice  around  the  muffle  to  the  center  and  down  into  the 
recuperator.  The  hottest  parts  of  the  flames  from  the  two  burn- 
ers applied  to  each  muffle,  moving  in  opposite  directions,  encircle 
the  muffle  ends  first,  then  encircle  the  middle,  thereby  neutraliz- 
ing the  "cold  end"  effect  and  giving  a  more  uniform  muffle 
temperature. 

Figure  11 :  Battery  of  four  drop-frit  furnaces :  Each  fur- 
nace is  fired  by  two  small  gas  burners  made  from  pipe  fittings. 
The  gas  and  air  are  preheated  in  wrought  iron  pipe  coils  placed 
in  the  outgoing  flue.  The  flames  pass  into  the  combustion  ring 
tangentially,  then  pass  over  a  flash  ring  and  down  around  the 
crucible.  The  frit  pan  underneath  when  filled  with  water  forms 
a  "water  seal."  The  bottom  of  the  pan  is  curved  so  that  the 
frit  can  be  raked  out,  making  it  unnecessary  to  remove  the  pan. 
The  principal  objection  in  the  construction  of  the  furnace  is  that 
the  frit  pan  is  too  close  to  the  fire.  It  should  be  placed  about 
two  to  three  courses  of  brick  lower  in  order  to  obviate  the  rapid 
evaporation  of  the  water  and  the  burning  of  the  top  of  the  pan. 

Ceramic   Laboratories. 

University  of   Illinois 

DISCUSSION 

Mr.  Blair:  Will  Professor  Stull  give  us  an  idea  of  the  cost 
of  bui'iiing.  that  first  kiln? 

Prof., Stull:  Yes.  I  can  give  you  an  idea  of  the  cost.  Like 
Professor  Bleininger,  I  did  not  want  to  scare  you  to  death  with 
the  figures.  A  large  fill  was  made  on  the  present  site  of  the  new 
kiln  house.  In  building  the  foundations  for  these  kilns,  it  was 
necessary  to  go  down  so  deep  to  get  solid  ground  that  it  brought 


DESIGNS  OF  SEVEN  TEST   KILNS  9 

up  t lie  casts  enormously.  The  cost  of  that,  pari  below  ground  is 
nearly  as  much  as  that  above  ground.  The  first  furnace  shown 
cost  between  seven  hundred  and  eight  hundred  dollars,  that  is, 
as  near  as  I  can  remember.  The  figure  given  is  for  the  kiln 
complete,  including  foundation,  dues,  iron  work  and  all.  Plenty 
of  iron  work  has  been  placed  on  all  kilns  with  a  view  to  having 
them  well  braced. 


1.0 


DESIGNS  OF  SEVEN  TEST  KILNS 


Q    Z 

uJ    -1 

s  2 

1 

li-    f- 

_J    -O 

—     UJ 

O  P 

DESIGNS  OF  SEVEN   TEST    KILNS 


11 


Fig.    6 


12 


I)    SKiXS    OF    SKVKX    TEST    KILNS 


'^HHHhHHH 


DESIGNS  <»F  SEVEN   TEST    KILNS 


13 


14 


designs  ok  Seven  tkst  kilns 


<&                ' 

■                  * 

■-  - 

f*fi 



^L 

- 

. 

y                  k  ....          ^ .  sl_ 

DESIGN'S  OF  SEVEN   TF.KT    KII.NM 


15 


^^MBESSaMm 


HHHHHHHHHHMHhHHhHH 


L*4 


t*: 


16 


DESIGNS  OF  SEVEN  TEST  KILNS 


UNIVERSITY  OF  ILLINOIS  BULLETIN 

I  S  S  V  E  I)     W  E  E  K  L  Y 

Vol.  XI.  JULY  6,   1914.  No.  45 

[Kntered    as    second-class    matter    December    11,    1912,    at    the    post    office    at 
Urbana,    Illinois,    under  the   Act   of  August   24,    1912.] 


BULLETIN  No.  21 
DEPARTMENT  OF  CERAMICS 

R.   T.    STULL,   Acting  Director 


DEFORMATION  TEMPERATURES  OF 
SOME  PORCELAIN  GLAZES 

BY 
R.   T.   STULL  and  W.   L.   HOWAT 


A  TYPE  OF  CRYSTALLINE  GLAZE 
AT  CONE  3 

BY 
C.   C.   RAND  and  H.   G.   SCHURECHT 


PUBLISHED   BY  THE  UNIVERSITY  OF  ILLINOIS,   URBANA 


19  13-1914 


W  THE 


Authorized    Reprint    from    Volume   XVI,    1914,    fransactious    \ tear   Ceramii    3 


DEFORMATION   TEMPERATURES   OF  SOME 
PORCELAIN  GLAZES 

K.   T.   STILL    A.ND   \V.    L.    HOWAT,    I'KBAXA,   ILL. 

The  group  of  glazes  studied  comprises  ten  horizontal  series 

designated  by  letters  from  A  to  J,  each  series  consisting  of  ten 
members.  The  group  of  one  hundred  members  covers  the  fol- 
lowing limits  represented  by  the  four  corner  glazes  : 

TABLE  I  — FORMULA  OF  CORNER  GLAZES 


GLAZE 

K.O 

CaO 

\!  ii 

SiO. 

\-l         

0.3 
0.?. 
0.3 
0.3 

0.7 
0.7 
0.7 
0.7 

0.40 
0  .  40 
0.85 
0.85 

2.0 

A-10    

6.5 

T-l      

2.0 

T-io    

6.5 

TABLE  II  — BATCH  WEIGHTS 


BRANDY- 

WINE 
FBIiDBPAB 

WHITING 

Rate.  No. 

20      BALL 
CLAY 

N.     C. 
KAOLIN 

FLINT 

AUOH), 

A-l     

167.4 
167.4 
167.4 

167.4 

70.0 

70.0 
70.0 
70.0 

12.!) 
1 2  .  9 
12.9 

70.9 

12.9 
12.9 
12.9 
70.9 

270.0 
216.0 

A-10     

T-l    

70.2 

T-10    

Different  members  in  the  group  were  made  by  molecular 
blending  of  the  four  extremes.  These  were  applied  to  bisque 
wall  tile,  set  in  saggers  in  a  down  draft  kiln  and  burned  to  cone 
!>  in  40  hours. 

('ones  were  also  made  from  the  glazes  and  their  deforma- 
tion temperatures  determined  in  a  platinum  resistance  furnace, 
the  temperatures  being  measured  by  a  platinum,  platinum-rhod- 
ium thermocouple  and  a  Leeds-Northrup  direct  reading  poten- 
tiometer,  (accurate  to  3  G). 


4  DEFORMATION    TEMPERATURES    OF    GLAZES 

The  time-temperature  curve  followed  in  all  determinations 
is  shown  in  Figure  1.  The  temperature  was  raised  to  1200°C. 
in  120  minutes.  Beyond  this  the  temperature  rise  was  2^  de- 
grees per  minute.  A  number  of  deformation  tests  made  on  du- 
plicate Seger  cones  gave  the  following  results:  cone  4  —  1212°C, 
cone  6— 1255°C,  cone  8-1290°C. 

Deformation-temperature  readings  were  made  on  two  or 
more  cones  of  each  glaze.  The  variation  was  rarely  over  5  C. 
and  in  the  majority  of  tests,  duplicate  cones  gave  the  same  tem- 
perature readings. 

TABLE    III  — DEFORMATION    TEMPERATURES    COVERING    THE     LIMITS 

''■:;!>(,'   '  0.40  to  0.85  AUO:,   :   2.0  to  6.5  SiO, 
O.i    Cat)   i 


ALO, 

I    i    I    !    I    I    I    I    i    1    I -__ 

J     1277  1246  L232  r235  1 247il252|1248!l260J1267il26o|    0.85 

i  1275]1240|I228!1230|1240|1235|1245|1247I1250[1252     0.80 

H   1272  1245  12:52  12X0  1  230  '1232  12X51235  1245  1245     0.75 

G  |l272il240|l228|l228|l232Jl232Jl233|l2::7  1235  1247     0.70 

F  126711238  1225  1225  1225  1225J1228|123"5  1235  1245     0.65 

E  1232  1225  1225  1222  1220  1225  1228  1235  1245  1245     0.60 

D  1230J1225  1225  1227|l230  1230il24o|l245|l248  1252     0.55 

C  1232  1228  1228  1228  1228  1230  1240  1248|l252|l255     0.50 

B  |1235|1230  1228  1233|l235!1245  1254  1252  1257Jl270J    0.45 

A  1232  123,2  1240  1245  1245  1255  1255  1268  1272  1277     0.40 


M  LECULES 

si0      2.0  2.5|  3.0,  3.5  4.0  4.5  5.0  5.5  6.0|  6.5! 


The  average  temperature  readings  for  two  or  more  cones  of 
each  glaze  of  the  group  are  given  in  Table  III.  The  results  of 
the  burn  and  the  iso-deformation  lines  are  represented  graphi- 
cally in  Figure  2,  the  deformation-temperature  being  indicated 
in  degrees  centigrade  on  each  line. 

The  RO  is  constant  for  all  glazes.  The  molecular  variations 
of  Si()„  are  plotted  along  the  abscissa  and  the  molecular  varia- 
tions of  ALO,  on  the  ordinate. 


DEFORMATION    TEMPERAT1  KM  S   OF  GLAZES 


Q 

Q 

fc 

ti 

^ 

^ 

5 

& 

* 

B) 

i\ 

v 

SL  3&frUMU3ctH/JJ. 


6  DEFORMATION    TEMPERATURES   OF   (iLAZES 

In  the  lower  right  corner  are  the  devitrified  glazes  between 
the  limits : 

RO,  0.4Al2O3,  5.0SiO2 
BO,  (UAlJL  6.5Si02 
RO.  0.6Al2O3,  6.5Si02 

In  the  lower  portion  of  the  devitrified  area  the  glazes  were 
'■razed.  In  the  center  of  the  field  are  the  brigUrt  glazes  which 
were  considered  matured.  Bright  glazes  which  were  crazed  are 
found  in  the  lower  left  corner  within  the  limits: 

RO,  IUALO,,  2.5Si02 
RO.  (UA1,03,  2.0SiO2 
RO,  0.5Al2O3,  2.0SiO~ 

At  the  left  of  the  field  a  small  group  of  matured  mats  are 
found  between  limits  : 

RO,  0.55Al2O3,  2.0  SiO, 
RO,  0.70  A1203,  2.0  SiO^ 
RO,  0.65  Al,o:,  2.5Si02 

In  the  upper  part  of  the  field  the  glazes  were  under  fired. 

The  difference  between  max  and  n:in  deformation  tempera- 
tures is  57  ('..  the  softest  one  deforming  at  1220°C.  having  the 
formula,  RO,  0.6  ALO,,  4.0  Si02.  The  member  at  the  upper  left 
corner  (RO,  0.85  ALO,,  2.0  SiO.,)  and  the  one  at  the  lower  right 
corner  (RO,  0.4  ALO.,,  6.5  Si02)  deformed  at  the  max  tempera- 
ture 1277  C. 

Each  horizontal  scries  may  be  considered  as  being  com- 
posed of  the  components,  glaze  and  SiO.,.  The  broken  line 
CD  passes  through  the  deformation-eutectic  of  each  of  the  ten 
p'laze — Si02  series.  In  a  vertical  direction,  consider  each  series 
made  up  of  glaze  and  A1203,  the  dotted  line  EF  represents  the 
deformation-eutectic  axis  of  the  ten  glaze — ALO,  series. 

These  two  axes  (CD  and  EF)  cross  at  the  point  of  lowest 
deformation  temperature  (group  eutectic).  Its  deformation 
temperature  is  ten  degrees  higher  than  the  indicated  tempera- 
ture of  Seger  cone  4.  The  glazes  whose  formulae  correspond  to 
cones  4,  5  and  6  deformed  at  1228  O.  1240^C  and  1245°C  re- 
spectively. 


DEFORMATION    TEMPERATURES   <>K  GLAZES 


The  line  AB  is  the  higih  gloss  axis  plotted  according  to  the 
appearance  of  the  glazed  trials.  The  gloss  axis  follows  roughly 
parallel  to  thr  glaze-Si<  >2,  deformation-eu<teetic  axis  up  to  the 
group  cuteetie.     Beyond  this  point  it  deflects  and  follows  along 


T/?a/vs.  am.  ce/?soc  i/t?i.  xw 


r/G.- 


src//.L  &  hcw 


s.£         4.0 


C0M£  A///V£  BUffN 
\  .3t$0 


g/P/GHT 
MATT 


\  1   "<M*Tl/#£ 


PEVtT/?//*/£0 

CtfAzeo 


P£WTf?/FIE0 
C/ZAZ£D 


the  glaze- A1203  deformation-eutectic  axis.  The  group  deforma- 
tion-eutectic lies  near  the  center  of  the  field  of  best  glazes,  and 
the  quality  of  the  glazes  decreases  in  all  direction  away  from 
this  euteetic  point.  The  genera]  formulae  of  the  best  glazes  as 
shown  hv  the  trials  are: 


DEFORMATION    TEMPERATURES    OP   GLAZES 

RO-0.60A1,<),  4.0  Sin,  Deformation  temp.  —  1220°C. 

Ro-o..-).-)  A L,<>,  3.5SiQ2  Deformation  temp.  ==1227  C. 

BO-0.55  A12Q3  4.0  SiO.  Deformation  temp.  =  1230°C. 

KO-0.60  ALO,.  3.5  SiO,  Deformation  temp.  =  1222 °C. 


T&AMS.  s4M.  C£/?.  SOC.  l/OL .  XW 


STVLL  &  HO  WAT 


.20 


3  6  4.Z 

MOLecoies      s,o. 


come  eleye/v  burn 
constant  { 

.7  CO 


SOCWD 
CtfAZED 


The  difference  between  the  deformation-temperatures  of 
the.se  glazes  and  the  temperature  to  which  they  were  fired  (cone 
9)  is  80'  C  to  9.0  C,  or  a  difference  of  4  to  4U  cones.  For  the 
purpose  of  comparison  the  iso-deformation  temperature  lines  are 
plotted  on  the  field  of  porcelain  glazes  burned  at  cone  11  and 


DEFORMATION'    TK.M  l'KKATl   RKS    OF    ©LAZES  9 

jn-o\i( ut>l \-  reported,1  Figure  3.  The  high  gloss  axis  QT  lies  to 
the  righl  '»i  the  glaze-SiOj,  eutectie  axis  and  crosses  the  glaze- 
AL<>.  eutectie  axis  close  to  the  eutectie  member  of  the  group. 
The  besl  glazes  in  this  group  arc  found  in  close  proximity  to  the 
group  eutectie,  the  same  as  in  the  cone  !'  burn.  Not  only  docs 
the  group  eutectie  lie  near  the  center  of  the  area  of  besl  glazes, 
but  it  is  also  Located  at  a  safe  distance  away  from  devitrification, 
crazing,  matness  and  immaturity. 

Ceramic    Laboratories, 

University   of   Illinois. 


1  Influences    oi    variable    silica    and    Alumina    on    Porcelain    Glazes    of    Constant    RO, 

Trims.    Amrr.   Cer.   Soc,   Vol.   xiv,   pp.   62-70. 


A  TYPE  OF  CRYSTALLINE  GLAZE  AT  CONE  3 


C.  C.  RAXD  AND  II.  G.  SCHURECHT,  1RBAXA,  ILL. 

The  glazes  under  consideration  are  of  a  type  designed  to 
mature  about  cone  3  to  4.  The  A1203  is  maintained  constant 
throughout  at  .05  equivalent  and  is  introduced  as  Pikes  No.  20 
English  ball  clay.  In  general  the  group  resembles  Worcester's1 
best  raw  clay  glaze.     His  formula  was 

0.33%  Na20         |        n_Q  |  1.60  Si02 

O.662/3  ZnO  }       )m       '■>  )  0.20  B203 

He  concludes,  however,  that  .05  A1,03  generally  seems  the  most 
favorable  and  that  many  German  formula?  call  for  this  amount. 
A  group  of  36  glazes  was  made  with  a  view  to  determine  the 
effect  of  varying  ZnO  against  Na20  along  the  ordinate,  and  rutile 
against  Mint  along  the  abscissa. 


0SC00)  303*°3\ 


fro./ 


ffl)^f{— 


.a<sc<70 


c 

'        ^ 

t       4 

<■        J 

_         6 

■'Zs&oJJO&Oj     \0.S77O£ 


6  .SOA,c7^o\.a5/J^Oj  {/.S5/Ot 
0SO70)  s  I  * 


The  arrangement  of  the  group  with  the  formulae  of  the  four 
corners  are  shown  in  Fig.  1,  the  vertical  series  being  designated 
by  numbers,  the  horizontal  series  by  letters. 

Two  frits  of  the  following  compositions  were  used : 

No.  1 
0.25  Na,0    | 

0.70  ZnO     1 0.30  B203    [     1.4  Si02 

0.05  OoO 


'  Vol.    \    Trans.   Amer.   Cer,   Soc,   p.   150.      Function  of  Alumina   in  Crystalline   Glaze. 


CRYSTALLINE  <  LAZE  AT  CONE  3  11 

No.   2 
0.50  \';i,0    I 

0.45  ZnO     1 0.30  B,03    ;     1.4  SiOa 
0.05  CoO     I 

These  we're  each  intimately  mixed  and  ground  in  small  ball 
mills,  fused,  quenched  in  water,  dried  and  ground  to  pass  80 
mesh  sieve. 

The  four  corner  glazes  were  ground  wet  until  they  passed 
1l!<)  mesh  sieve,  and  the  remaining  glazes  blended  from  them  in 
molecular  proportions. 


I 

/ 

1 

47 

1 

; 

*  600 
\ 

\S°° 

8  *°° 

15   JOO 

zoo 
/oo 

0 

' 

1      J 

I 

; 

i 

77/7 

/ 
'e  //7 

/Ycc// 

'       / 
s 

»      /. 

7        7 

4      /. 

f      ft 

f       / 

y    /i 

?    /. 

?       Zo 

The  glazes  were  applied  to  two  sets  of  biscuit  tile  by  dip- 
ping, and  burned  to  cone  3  in  5  hours  in  a  round,  down-draft. 
open-fired  oil  kiln.  The  fires  were  put  out  when  the  finishing 
temperature  was  reached  and  the  kiln  allowed  to  cool  with  the 
damper  closed. 

The  results  were  not  satisfactory,  as  only  a  few  crystalline, 
patches  appeared.  These  pitches  increased  noticeably  as  the  con- 
tent of  ZnO  increased.  High  ZnO  also  appeared  to  give  a.  deeper 
blue  ;is  wonld  be  expected.     B  3  showed  the  most  crystallization. 


12 


CRYSTALLINE  GLAZE   AT  CONE  3 


1 

5 


^ 


^ 


^ 


^ 


M 


CRYSTALLINE  GLAZE  AT  CONE  3  13 

Tin*  failure  bo  obtain  good  results  was  attributed  to  too  rapid 
cooling,  boo  thin  coating  of  the  glaze,  and  perhaps  slight  under 
burning. 

Next  two  sets  of  trials  were  dipped,  care  being  taken  bo  ob- 
tain a  thick  coating  of  the  glaze,  and  burned  in  the  same  kiln  to 
cone  4.  following  the  beating  and  eOoling  curve  shown  in  Figure 
2.  The  pyrometer  showed  a  temperature  of  1170:,C,  when  cone 
4  went   down. 

From  a  crystallization  standpoint,  the  results.  Fig.  3,  were 
highly  satisfactory.  Every  glaze  showed  a  large  number  of  crys- 
tals and  in  many  cases  was  a  solid  mass  of  crystals  of  varying 
sizes.  The  variation  of  ZnO  and  Xa.,0  seems  to  have  little,  if  any, 
effect  upon  either  crystallization  or  color. 

Increase  in  Ti02  has  a  marked  effect  upon  both.  As  TiCL 
increased  the  crystals  became  smaller,  and  more  numerous,  most 
of  the  high  rutile  glazes  consisting  of  a  mass  of  small  interlocking 
crystals.  At  0.0  Ti02  and  at  0.1  TiO,,  a  good  blue  color  is  shown. 
but  from  0.1  Ti02  up,  the  blue  is  partially  and  in  some  cases  al- 
most totally  absent.  Bronze  patches  are  quite  prominent,  due 
possibly  to  iron  impurities  in  the  rutile. 

The  two  sets  of  trials  are  very  nearly  identical.  Glaze  E  3, 
with  the  formula 

°nf.  "«£     |     0.05  AUK   j     1.8  SiO= 

again  appears  to  contain  the  most  crystals  and  for  this  reason 
was  selected  as  the  glaze  to  use  in  making  draw  trials  with  a  view 
to  noting  different  stages  of  crystallization. 

The  glazes  were  dipped  and  burned  in  the  same  manner  as 
before,  a  number  of  trials  of  E  3  being  placed  where  they  could 
be  drawn.  .  One  was  drawn  at  the  finishing  point,  and  one  every 

20     as  the  i Ling  progressed.     The  third  trial  drawn  showed 

crystals  around  the  edges.  The  amount  of  crystallization  in- 
creased steadily  for  four  trials.  The  next  trial  at  1030°C  showed 
a  very  great  increase,  the  glaze  consist  inn-  of  a  mass  of  crystals. 
It  is  posible  that  this  is  due  to  the  crystallization  of  an  eutectic. 


14 


CRYSTALLINE  GLAZE   AT  CONE  3 


That  is,  the  compound  forming  the  crystals  shown  first  continued 
crystallizing  out  until  the  melt  reached  the  composition  of  the 
euteetic  mixture,  when  the  whole  mass  crystallized.     (Fig.  4.) 


TRAA/S.Aa^.C^/^.SOC.  yOL.XW       /V<5.^         /ZA/V0&  SC/SCfPECHT 


//70°C 


/070°C 


/050°C 


/030°C 


/o/o  °o 


One  set  of  trials  was  placed  on  edge  in  this  last  burn.  They 
failed  to  show  as  much  crystallization  as  those  lying  down,  as  the 
glaze  had  run  off  to  a  great  extent.  However,  good  results  were 
obtained  on  two  small  vases  to  which  the  glaze  had  been  applied 
in  a  very  thick  coat,  though  here  also,  much  of  the  glaze  had  been 
lost. 


UNIVERSITY  OF  ILLINOIS  BULLETIN 

ISSU  E  D     W  E  E  K  1.  Y 

Vol.    XI.  JULY   13,    1914.  No.   46 

[Entered    as    second-class    matter    December    11,    1912,    at   the   post   office   at 
I'rbana,    Illinois,    under  the    Act   of  August   24,    1912.] 


BULLETIN  No.  22 
DEPARTMENT  OF  CERAMICS 

R.    T.    STULL,   Acting  Director 


THE  INFLUENCE  OF  CHLORIDES  OF  CAL- 
CIUM AND  IRON  WHEN  PRECIPITATED 
IN  A  PORCELAIN  BODY 


SOME   COBALT-URANIUM   COLORS 

BY 
B.   S.   RADCLIFFE 


PUBLISHED  BY  THE  UNIVERSITY  OF  ILLINOIS,   I'RBANA 


19  13-1914 


Authorized    l.'.-prini    from    Volume    XVI,    L914,   Transactions   American   Ceramic  Society 


THE  INFLUENCES  OF  CALCIUM  AND  IRON  CHLOR- 
IDES PRECIPITATED  IN  A  PORCELAIN  BODY 

I'.Y    li.   s.    RADCLIFFE 

The  production  of  vitrified  red  floor  tile  has  given  manu- 
facturers considerable  trouble.  Pra  'dually,  the  only  solution  <>!' 
the  problem  1ms  been  to  secure  <i  good  red  burning  clay,  and 
burn  to  a  degree  of  vitrfie:rion  such  that  the  red  color  is  not  de- 
stroyed. In  most  instan<  s.  ir  has  been  found  impossible  to  make 
red  bodies  that  have  I  s  than  four  or  live  percent  absorption, 
and  in  many  cases  he  absorption  is  considerably  greater  than 
this. 

Good  red  bodit*  can  he  made  by  mixing  the  proper  amounts 
of  feldspar  and  flint  with  "  FTebnstadter"  clay,  and  burning  to 
practically  complete  vitrification. 

This  clay  is  very  line  grained,  plastic,  and  is  red  in  color. 
The  original  red  color  of  the  clay  is  only  slightly  altered  during 
burning,  up  to  the   point  when   the   porosity  is   reduced   to  about 

three  percent.  A  higher  temperature  causes  the  red  color  to 
deepen  and  gradually  change  to  dark  brown  and  finally  black. 
The  deepening  of  the  color  begins  about  cone  6,  and  by  cone  S 
the  body  is  dark  brown  to  black.     The  burning  qualities  of  this 

day   seem    to   be   due   to   the    fact    that    the    iron    is    present    in    a 

highly  disseminated  state. 

This  investigation  was  made  to  determine  whether  uniform 
colors  of  iron  in  varying  shades  could  be  produced  by  precipi- 
tating the  chlorides  of  iron  and  calcium  in  a  body. 

A  cone  10  porcelain  was  chosen  for  the  body.  It  is  not 
considered  an  ideal  one  for  the  production  of  vc{]  tile,  and  one 
containing  more  ball  clay  in  place  of  the  china  clay  would  prob- 
ably be  better,  since  it  would  have  less  porosity  in  the  (\vy  state 
and  would  require  less  fluxing  action  for  complete  vitrification 
on  that  account. 

Procedure.  The  three  corner  bodies  ;is  shown  on  the  tri- 
atrial diagram  were  mixed  by  wet-grinding  for  five  hours  in  a 
porcelain-lined  ball-mill.  The  tri-axial  group  of  66  bodies  was 
made  by  blending  these  three  bodies. 


CALCIUM    AND    [RON    CHLORIDES    IX    PORCELAIN    BODY 


CALCIUM    AND    [RON    CHLORIDES    l\    PORCELAIN    BODY  3 

The  mixtures  were-  put  in  fruit  jars  and  shaken  thoroughly 
so  as  to  obtain  uniform  mixtures.  The  chlorides  were  precipi- 
tated by  adding-  XII, Oil  and  I .  X  1 1 ,)_.('( >..  and  shaking.  The 
slips  \\\'ix>  allowed  to  stand  for  a  day,  after  which  tlhey  were 
poured  into  plaster  molds.  When  the  excess  water  had  been  ab- 
sorbed the  bodies  were  removed  6rom  the  molds,  and  dried  in  an 
oven  to  200  0.  After  crushing  in  a  porcelain  mortar,  triangular 
floor-tile  were  made  by  the  dry-press  prooess,  about  LO  percent  of 
water  being  used.  They  were  burned  DO  cones  5,  7,  9  and  11  in 
an  open,  down-draft,  gas-fired  tesl  kiln. 

Results.  Those  bodies  high  in  iron  were  most  plastic,  and 
those  high  iu  lime  were  least  plastic.  This  was  shown  both  by 
the  working  properties  of  the  bodies  in  I  he  plastic  slate  and  by 
I  lie  strength  of  the  dried  tile. 

Vitrification — None  id'  the  bodies  were  completely  vitrified 

at  cone  5,  although  tho.se  high  in  iron  and  lime  were  hard  anil 
dense,  those  high  in  lime  being  the  hardest.  At  cone  7.  all  bodies 
containing  over  four  percent  of  fluxes  were  vitrified.  All  bodies 
were  completely  vitrified  at  cone  9,  those  containing  over  7  per- 
cent of  fluxes  being  overburned. 

Bodies  containing  4  percent  and  over  of  fluxes  were  over- 
burned  at  cone  11.  The  remainder  retained  their  shape  but  had 
a  glassy  surface  with  the  exception  of  1,  2  and  3. 

Color — Bodies  Tree  I'roni  iron  burned  white  and  were  prac- 
tically uniform  in  color  at  vitrification. 

Those  containing  1  percent  of  iron  were  cream  colored  when 
burned  under  oxidizing  conditions,  but  a  good  uniform  gray 
color  was  obtained  when  the  tile  were  reduced  at  the  end  of  the 
burn,  'fhe  lime  had  very  little  effect  upon  the  color  of  bodies 
containing  1  percent  of  iron.  Bodies  containing  '_'  percent  of 
iron  were  pink  or  light  red  at  cone  5,  above  which  temperature 
they  changed  to  brownish  buff  with  the  exception  of  No.  4.  which 
became  dark  yellowish  may. 

Bodies  containing  4  to  111  percent  of  iron  burned  n'i\  to  dark 
rr(\  at  cone.").  Those  containing  I,  .">  and  ti  percent  were  still  red 
at  cone  7.     The  color  was  much  deeper  than  at  cone  5  and  in- 


4  CALCIUM     \XI>    [RON    CHLORIDES    IX    PORCELAIN   BODY 

creased  with  increased  iron.     Two  percent  of  lime  did  not  affect 
the  color  of  bodies  containing  5  percent  or  over  of  iron. 

The  remainder  of  the  .series  did  not  produce  desirable  colors 
for  floor  tile. 

CONCLUSIONS 

Uniform  gray  colore  of  pleasing  shades  can  be  made  by  pre- 
cipitating 0  to  -  percent  of  iron  in  a  porcelain  body  and  burning 
properly. 

Uniform  red  colors  can  be  produced  by  precipitating  4  to  6 
percent  of  iron  in  a  porcelain  body  which,  if  burned  properly, 
would  not  have  more  than  3  to  4  percent  porosity. 


( leramic  Laboratory, 

University    of    [llinois 


DISCUSSION 


Mr.  Parmelee:  1  should  like  to  ask  the  reason  for  using 
calcium  salt. 

Mr.  Eadcliffi  :  Calcium  chloride  was  added,  because  it  is 
a.  soluble  salt;  ami  it  was  thought,  that  the  intimate  mixture  of 
the  calcium  and  iron  obtained  in  this  way,  might  throw  some 
light  on  the  cause  of  the  varied  color  effect,  produced  by  iron  in 
different  clays. 


SOME   COBALT-URANIUM   COLORS 
r.Y    B.   s.   RADCLIFPB 

Then-  are  four  coloring  oxides,  namely,  copper,  chromium, 
nickel  and  iron,  which  under  proper  conditions  produce  green 
colors  in  bodies  and  glazes.  In  physical  mixtures,  uc  are  able  to 
produce  greens  by  blending  blue  and  yellow. 

The  object  of  this  investigation  was  to  determine  whether 
green  could  be  produced  by  blending  cobalt-blue  and  uranium- 
yellow. 

Series  A  was  made  up  as  follows: 

TABLE    I— SERIES    A 


Co*03 

Na2U20,  <;H,0 

Al,(OH), 

ZnO 


1.0 
50.0 
40.0 
25.0 


0 . 9 

50 . 0 
40.0 
25.0 


0.8 
50.0 
40 . 0 
25.0 


0.7 
50.0 
40 . 0 
25.0 


0.G 
50.0 
40.0 
25.0 


The  stains  wwt'  thoroughly  mixed,  calcined  to  cone  5,  ground 
to  pass  a  200  mesh  screen  and  added  to  a  mat  glaze  having-  the 
formula, 

0.1  K,()     ) 

0.2  OaO    I    0.36  AL<),     1.36  Si<>_. 

0.7  PbO    J 

The  glaze  was  then  burned  to  cone  05.    The  result  was  a  yellow- 
ish green  glaze  with  blue  specks.    This  was  due  to  the  fad  that 
the  cobalt  was  not  thoroughly  disseminated. 
A  hi uc  stain 

Gov,Oa    10 

("ale.    A1208     45 

ZnO   4o 

was   then    made,   calcined    to   cone   7.   and    ground    to    pass   a    200 
mesh  screen. 

Three  frits  were  made  using  the  mat  glaze  as  before. 


SOME   COBALT-URANIUM    COLORS 
TABLE    II— SERIES     B 


Bi 

u„ 

B. 

Feldspar 

17.6 
6.3 
50.5 
11.0 
10.0 
4.6 
10.0 
25.0 

17.6 

6.3 

50.5 

11.0 
10.0 
4.6 
10.0 
35.0 

17   6 

CaCO 

6   3 

Red  lead    

Kng'.   china  clay 

50 . 5 
11   0 

Tenn.  ball   clay 

Flint 

10.0 
4   6 

Blue    stain 

10   0 

45.0 

When  applied  as  glazes,  B  1  gave  an  olive  green,  B  2  and 
B  3  rich  chocolate  browns.  These  results  indicate  that  the  ratio 
of  uranium  to  cohalt  is  too  high. 

The  next  step  tried  was  to  use  the  nitrates  of  cobalt  and 
uranium,  bv  Fritting  in  the  mat  glaze. 


TABLE     III— SERIES    C 


Feldspar 

CaCO:, 

Red   lead    

Eng\  china   clay 
Tenn.   ball    clay. 

Flint 

Cobalt   nitrate    . 
Uranium   nitrate 


17.6 

17.6 

17.6 

6.3 

6.3 

6.3 

50 . 5 

50.5 

50.5 

11  .0 

11.0 

11.0 

10.0 

1 0 . 0 

10.0 

4.6 

4.6 

4.6 

3.5 

3.5 

3.5 

10.0 

1  2  . 0 

15.0 

The  frits  were  ground,  and  a  scries  of  glazes  made  by  blend- 
ing with  the  original  mat  glaze. 

Bright  glazes  were  made  by  adding  20  parts  of  flint  to  the 
frits  of  this  series. 

The  mat  glazes  were  olive  green,  C,   having  a  bluish  shade. 

Of  the  bright  glazes  C3  was  dee])  green  in  color,  and  Ca  and 
(\,  were  green  witli  a  bluish  shade. 


SOM  E  COBALT-1  RANI1   M    COLORS 

Conclusions:  Green  glazes  and  ruiats  ean  be  made  by  blind- 
ing cobalt  iin.l  uranium  in  the  right  proportions,  which  is  be- 
tween four  ;ui(l  five  parts  of  uranium  nitrate  to  one  pari  of  co- 
ball   uitrate. 

<  Vramic    Laboratory . 

University    of    Illinois. 

DISCUSSION 

Prof.  Orion:  1  do  aot  know,  whether  there  has  ever  been 
any  report  made,  aboiri  the  peculiar  green  developed  by  one  of 
the  roofing-tile  plants  in  this  country  by  the  use  of  eoball  oxide 
and   sulphate  of  antimony.     These   coarsely   ground    chemicals 

were  added  to  a  roughly  prepared  glaze;  and  the  result  was  thai 
they  succeeded  in  getting  a  very  passable  green.  At  least  it 
looked  like  a  good  green  on  the  roof,  but  if  looked  at  close  by, 
the  size  of  the  blue  and  yellow  spots  was  so  Large  as  to  be  offen- 
sive. The  reason,  that  they  did  this,  was  that  they  were  working 
in  a  sulphurous  close  atmosphere,  thai  spoiled  other  greens,  and 
they  thought,  that  if  they  had  a  sulphate  to  start  with,  it  would 
not  do  any  harm. 

Mr.  Uadcliffe:  T  might  say  that  a  man  in  the  berra-eotta 
business  in  Kansas  told  me  that  In1  used  cobalt  and  uranium  to 
produce  greens.  He  did  not  tell  me.  however,  until  we  worked 
it  out.  lie  was  using  it  for  polychrome  work.  The  cobalt-uran- 
ium green  that  he  produced  was  better  than  any  other  green  that 
he  could  make  for  this  purpose.  It  did  no;  run  or  blend  off  with 
the  white,  but  instead  he  could  <:"<jt  a  firm  line  between  the  green 
and  the  white,  or  whatever  base  was  beneath  the  green  poly- 
chrome work'. 


a3 


UNIVERSITY  OF  ILLINOIS  BULLETIN 

i  ssi'  i:  i)    \v  i:  i:  ki.i 
Vol.   XI.  .11  I.Y  30,    L914.  No.  47 

[Entered    as    second-class    matter    December    11,    1912,    at   the    post   office   at 
I'rbana,    Illinois,    under  the    Act   of  August   24,    1912.] 


BULLETIN  No.  23 
DEPARTMENT  OF  CERAMICS 

R.   T.   STULL,   Acting  Director 


NOTES   ON   THE   DEVELOPMENT  OF  THE 
RUBY  COLOR  IN  GLASS 

BY 

A.   E.   WILLIAMS 


PUBLISHED  BY    THE  UNIVERSITY  OP  ILLINOIS,   URBANA 


19  13-1914 


Authorized  Reprint  from   Volume   XVI,   1914,  Transactions  American  Ceramic  Socictj 

NOTES  ON  THE  DEVELOPMENT  OF  THE  RUBY 
COLOR  IN  GLASS 

BY   A.    K.    WILLIAMS 

The  term  •"ruby  glass"  is  applied  to  red  glass  colored  by 
the  use  of  copper,  gold,  selenium  and  in  some  cases,  flowers  of 
sulphur,  the  color  varying  considerably  in  intensity  and  shade. 
In  case  of  copper,  the  color  varies  from  amber  to  various  shades 
of  reds  to  brown  and  to  opaque  black.  With  gold  the  red  has  a 
rose  tint,  and  selenium  ruby  seems  to  be  a  brighter  red  of  vary- 
ing intensities.  The  red  from  sulphur  is  rather  unreliable,  in 
that  a  uniform  color  is  hard  to  obtain,  and  therefore  only  used 
for  lower  grades  of  glass. 

Copper  and  gold  reds  are  said  to  be  due  to  the  metals  in 
suspension  as  colloids. 

V.  Poschl1'  describes  the  preparation  of  Purple  of  Cassius 
from  gold,  and  shows  that  the  red  or  the  purple  gold-hydrosol 
may  be  obtained,  depending  upon  the  proper  electrolyte  present. 

Paal  s2  process  for  the  preparation  of  colloidal  solutions 
shows  that  a  red  or  blue  hydro-sol  of  copper  is  obtained,  depend- 
ing upon  the  properties  of  the  solutions. 

In  G.  Bredig's"  method  of  producing  colloids  electrolytically, 
he  obtained  finely  divided  metallic  gold,  dark  purple  in  color, 
when  the  arc  takes  place  under  distilled  water.  If  a  trace  of 
caustic  soda  is  added,  deep  red  color  is  obtained. 

That  copper  and  gold  are  in  the  same  condition  in  glass  as 
in  solutions  is  proven  by  the  use  of  the  ultra-microscope. 

Zsigmondy4  says  that  ruby  glass  will  become  red,  or  remain 
colorless  upon  slow  cooling  according  to  its  quality.  It  will  al- 
ways remain  colorless  on  chilling,  the  normal  red  color  generally 
being  brought  out  upon  reheating  to  the  softening  point;  (high 
lead  glasses  show  yellow  or  brown  instead  of  red).  The  coloring 
is  due  to  the  gold,  which  is  at  first  homogeneously  dissolved  in 


1  V.  Posehl.  Chemistry  <>/  Colloid 

2  Ibid,  p.  6G. 

3  Ibid,  p.  G7. 


2  DEVELOPMENT  OF  RUBY  COLOR  IN  GLASS 

the  glass,  later  separating-  out  in  the  form  of  ultra-microscopic 
particles  which  reflect  green  light. 

He  compares  this  phenomenon  with  devitrification,  and  re- 
fers to  Tammann's5  work  on  devitrification.  Tammann  shows 
that  the  speed  of  crystallization,  and  the  ability  to  crystallize  in- 
crease with  diminishing  temperature  from  the  melting  point  and 
then  decrease  again,  while  viscosity  steadily  increases.  Zsig- 
mondy  applies  Tammann's  results  to  ruby  glass  in  this  manner: 
"Ruby  glass  is  worked  several  hundred  degrees  lower  than  its 
melting  temperature.  At  the  working  temperature,  conceive  it  as  a 
super-saturated  crystalloid  solution  of  metallic  gold  and  the  smallest 
amicroscopic  particles  to  be  centers  of  crystallization,  it  will  at  once 
be  seen  why  ruby  glass  sometimes  remains  colorless  upon  simple 
cooling.  In  this  case  the  optimum  temperature  for  spontaneous 
crystallization  is  so  low  that  the  glass  is  very  viscous  and  the  speed 
of  crystallization  reduced  to  a  minimum.  If  by  reheating,  the  glass 
acquires  a  certain  mobility,  the  gold  separates  out  upon  the  nuclei 
present  which  by  growth  become  sub-microns,  visible  in  the  ultra- 
apparatus  and  turning  the  glass  red  or  darker." 

V.  Poschl6  says  that  gold  ruby  is  obtained  by  an  addition 
of  gold  chloride  to  the  glass  melt  from  which  particles  of  gold 
separate  out,  when  the  mass  is  quickly  cooled.  These  particles, 
however,  have  the  magnitude  of  amicrons.  so  that  the  glass  ap- 
pears colorless.  By  heating  anew  until  the  glass  becomes  soft, 
the  particles  grow  until  they  attain  the  size  of  ultra-microns,  to 
which  the  cause  of  the  red  color  is  traced.  The  preparation  of 
copper  ruby  glass  is  performed  by  an  analogous  method. 

Copper  ruby  has,  in  the  past,  been  made  by  a  process  known 
as  flashing.  This  process  is  described  somewhat  as  follows  by 
Rosenhain  :7 

"Flashing  glass  is  the  process  of  placing  a  very  thin  layer  of 
colored  glass  on  the  surface  of  a  more  or  less  colorless  glass  of  usual 
thickness.  This  is  generally  accomplished  by  taking  a  small  gather- 
ing of  the  colored  glass  on  the  pipe,  and  the  remaining  gathering  for 
the  piece  to  be  made  from  the  colorless  glass  pot.  When  this  glass 
is  blown,  the  ruby  glass  lies  in  a  thin  layer  over  the  inner  surface  of 
the  cylinder.  The  special  skill  required  is  in  blowing  this  layer  to  a 
uniform  thickness  to  obtain  a  uniform  color." 

4  Zsigmondy,  Colloids  and  the  ultra-viicroscopc,  p.  165. 

5  Tan. inarm,    /.rit.    far    Ehctro-chimi,    1904,    Vol.    10,    p.    532. 
I  Ibid   I,   p.   103. 

7  Walter   Rosenhain,   Glass  iianufacturi . 


DEVELOPMENT  OF  KIT.Y  COLOR  IN  GLASS  3 

The  necessity  of  flashing  is  due  bo  tihe  density  of  the  color. 
Copper  colors  are  so  dense  thai  many  glasses  are  opaque  when 
over  :!  nun.  thick,  the  color  depending  upon  the  composition  and 
rate  of  cooling.  However,  it  is  possible  to  control  the  density  of 
tlie  color  gomewhal  in  the  Hashed  ruby  glass  by  carefully  con- 
trolling the  temperature  of  working  the  glass  and  pate  of  cooling 
in  the  molds. 

These  Factors  tnusl  be  controlled  very  carefully  in  practice 
to  produce  uniform  results.  If  these  glasses  are  cooled  very 
quickly,  as  for  instance,  chilling  in  water  or  rolling  very  thin 
(2  nun.  thick)  on  an  iron  plate,  the  red  color  will  not  develop, 
or  at  least  shows  only  in  scattered  streaks.  By  reheating  at  defi- 
nite temperatures,  the  color  may  be  obtained  in  varying  degrees 
of  intensity  from  amber  to  opaque  black,  depending  upon  the 
temperature  to  which  the  glass  is  reheated.  Thus  it  will  be  seen 
that  the  temperature  and  rate  of  cooling  must  be  constant,  to 
produce  a  uniform  shade  of  red  when  this  color  is  developed 
during  blowing. 

At  the  present  time,  however,  copper  ruby  glass  is  being 
made  in  which  the  color  does  rot  come  out  in  the  pressing  or 
working,  but  is  brought  out  later  by  reheating.  The  density  of 
the  color  in  this  glass  is  very  much  less  than  the  flashed  ruby 
glass,  and  pieces  of  greater  thickness  can  be  easily  made.  The 
color  range  from  a  light  amber  through  reds  to  a  dense  opaque 
black-,  with  an  increasing  temperature. 

Available  literature  consulted  on  the  subject  gave  no  com- 
plete or  definite  methods  for  working  ruby  glass,  but  emphasized 
the  oecessity  for  care. 

The  following  are  some  formulae  and  directions  obtained: 

Gerner,8  gives  a  history  of  copper  ruby  glass  and  a  number 
of  mixes  with  methods  of  handling.  The  following  are  two  of 
1  he  batches  invert  bv  him  : 


Gei  oer,   "Gltus,"  p,    1 95 


DEVELOPMENT  OF  RUBY  COLOR  IN  GLASS 


GERMAN  COPPER  GLASS 
.      100.0  Sand 
25.0  Potash 
17.0  Borax 
2.5  Cu20 
5.0  Sn02 
0.2  Fe203 
2.5  Mn02 
0.5  Bone  ash 


Calculated    Formula11 


0.200  PbO 
0.390  K20 
0.120  Na20 
0.095  Cub 
0.079  MnO 
0.014  CaO 


0.0060  Fe203 
0.2500  B203 
0.0044  PoO, 


4.36  SiO, 
0.09  SnOo 


100  Si02 
50  Pb304 
25  K2C03 

5  NaNO, 


FRENCH  COPPER  GLASS 

This  batch  is  fused,  chilled,  dried,  ground 
and  mixed  with  1  Cu20,  1.5  Sn02,  5  cream 
of  tartar.  This  is  melted  and  blasted  one 
hour  during  melt. 


Calculated   Formula 

0.534  PbO 
0.346  K20 
0.074  Na20 
0.046  CuO 


3.900  Si<02 
0.034  SnOo 


Notes  on  ruby  glass  from  Sprecihsaial10  give  the  following 
by  translation  : 

"In  the  manufacture  of  ruby  glass  it  is  not  in  the  field  of  the 
furnace  man  to  control  the  color.  Repeated  fusion  and  cooling-  makes 
the  best  color,  and  the  color  does  not  depend  as  much  upon  the  per- 
cent of  coloring  oxide  in  the  mix  as  upon  the  temperature  of  the 
glass  while  working,  the  rate  of  fusion  and  rate  of  cooling  the  fin- 
ished piece."     The  following  hatch  is  given: 


"The  empirical   formulae  of  nil   glasses 
by    I  lie  writer. 

»°  Sprechsaal,  Feb.   6,   1913,  p.   92. 


riven   in   the   following   work   were   calculated 


DEVELOPMENT    OF    KI'MY    COLOR    IX    GLASS  5 

LIGHT    RED  DARK    REM 

Sand     loo.o  kg.  100.0  kg. 

Soda   ash    16.0  kg.  16.0  kg. 

Potash     Ki.o  kg.  16.0  kg. 

Borax     4.0  kg.  6 . 0  kg. 

Whiting     10.0  kg.  12.0  kg. 

Witherite    lo.o  kg.  lo.o  kg. 

Cu.O     2 . 0  kg.  4 .  o  kg. 

S11O2     2.0  kg.  4.0  kg. 

Fe2Oa    0.5  kg.  l.o  kg. 

Cream    of    tartar 0.8  kg.  1.3  kg. 

Calculated    Molecular    Formula 

0.385  Na20  ] 
0.210  K,o 
0.222  CaO 
0.110  BaO 
0.0(54  CuO 


0.0066  Fe203  13.63  Si02 
0.0660  B.,6..     [0.03  Sni) 


"The  manufacture  of  ruby  glass  demands  great  care  and  practice 
in  working.  This  is  especially  so  with  pressed  glass.  The  raw  hatch 
should  be  put  into  a  preheated  pot  and  melted  six  hours.  The  melt 
is  blasted  several  times  and  poured  into  cold  water  for  remelting  and 
refining.  If  the  pressed  pieces  are  not  colored  enough  they  can  be 
reheated.  The  mold  must  not  be  too  hot  to  allow  the  glass  to  cool 
too  slowly,  or  too  cold  to  chill  and  cause  the  pieces  to  crack.  The 
following  batch  is  also  given:"11 

Sand     100.0  kg. 

Potash     25 . 0  kg. 

Red    lead    25 . 0  kg. 

Borax     10.0  kg. 

Soda     5.0  kg. 

Cu,0    3.5  kg. 

SnO;     3.0  kg. 

Fe,0::    o.5  kg. 

MnO-.     0.5  kg. 

Cullet     25.0  kg. 

Cream    of   tartar    0.5  kg 


[bid    10,  p.   92. 


DEVELOPMENT    OF    RUBY    COLOR    IN    GLASS 

Calculated    Molecular    Formula 

0.2020  K20 

0.6230  PbO 

0.1010  Na20 

0.0668  OuO 

0.0079  MnQ* 


0.00418  Fe,0: 
r  0.07250  B.,0. 


2.310  Si02 
0.018  SnOo 


Rudolf  Hohlbaum1-  says  that  red  colors  may  be  obtained  by 
the  use  of  Cir.O,  selenium,  sulphur  and  gold,  but  is  most  ofteu 
obtained  from  Cu20.  He  gives  the  following-  batch  for  a  copper 
rubv  : 


100.0  Si(X 

31.0  K2C03 

16.0  CaCO, 

0.6  Cu20 

2.0  SnO, 


K2CO3=80  to  85  percent  pure 


Calculated   Formula 


0.536  K,0 
0.440  CaO 
0.023  CuO 


4.570  Si02 
0.041  SnO, 


Hohlbaum  says : 

"Concerning  the  mixing-  of  the  C112O,  I  wish  to  remark  that  it  is 
possible  to  obtain  the  ruby  color  with  0.4  percent  Cu20,  also  with 
0.8  percent.  However,  with  0.8  percent  of  the  batch  as  Cu;0  the  color 
is  so  dense  that  large  masses  are  not  workable.  As  such  a  small  quan- 
tity of  Cu=0  is  needed  to  make  ruby,  it  is  mixed  best  by  using  0.8  per- 
cent Cu-jO  and  SnO  with  half  the  batch  of  glass.  When  the  glass  is 
ready  to  blast  then  mix  the  batch  containing  0.8  percent  Cu^O  with  an 
equal  batch  of  crystal  glass,  and  a  0.4  percent  Cu^O  batch  is  obtained 
which  gives  a  weaker  color.  It  is  best  to  employ  SnO  as  a  reducing 
agent  to  insure  the  obtaining  of  a  ruby  color,  and  one  finds  from 
practical  experience  that  the  mix  must  contain  less  than  double  the 
quantity  of  Ctu-O  as  SnO.  If  this  is  not  sufficient  reducing  agent, 
cream  of  tartar  may  be  used  in  quantities  to  satisfy  all  conditions. 
Iron  scale  may  also  be  used  as  a  reducing  agent  but  the  pure  ruby 
color  is  then  changed." 


12  R.    Hohlbaum,    Seitgewasse    Uerstellung    Beatbeitting    vnd    Verziervng    dcs    Felnern 
Holglases,  p.   125. 


DEVELOPMENT  OF  RUB?  COLOB  IN  GLASS  / 

Hohlbaum13  gives  the  following  hatch  for  a  gold  ruby: 

Rose  Color 

Sand     100.0  kg. 

Potash     34.0  kg. 

Calcium    carhonate     17.0  kg. 

Gold     16.0  gms. 

Gold  must  be  brought  into  the  mix  in  a  very  finely  separ- 
ted  form,  best  in  solution  or  as  Purple  of  Cassius. 

To  get  the  gold  in  solution,  it  must  he  cut  into  small  pieces 
and  dissolved  with  aqua  regia.  The  gold  solution  is  poured  on 
part  of  the  mix.  and  this  mixed  with  the  balance  of  the  batch. 

In  the  heat  of  the  oven,  the  decomposition  of  the  gold 
chloride  takes  place  so  rapidly,  that  a  portion  of  the  gold  chlor- 
ide is  carried  away  undecomposed.  There  is.  therefore,  not  so 
much  gold  dissolved  in  the  glass  as  is  introduced,  and  the  color 
is  much  weaker  than  it  would  he,  if  all  the  gold  were  dissolved. 
It  is,  of  course,  reasonable  for  one  to  try  and  reduce  the  vapori- 
zation  of  the  gold  chloride  as  much  as  possible.  This  may  be 
done  by  pouring  the  gold  chloride  on  1  kgm.  of  sand  and  evap- 
orating to  dryness.  Then  mix  this  well  with  half  of  the  hatch, 
or  use  gold  purple  in  the  same  manner. 

According  to  Hohlbaum 's  experience,  either  phosphoric  acid 
or  barium  work  favorably  in  the  making  of  gold  ruby,  causing 
the  gold  to  separate  out  more  rapidly.  Without  either,  the  ruby 
is  too  light.  A  batch  for  making  a  rose  glass  with  a  violet  tinge 
with  the  use  of  barium  is  given. 

Rose   Glass   with   Barium 

Sand 100 . 0  kgm. 

BaCO*    10.0  kgm. 

93   percent   soda.    XaX'0 43.0  kgm. 

Gold    12.0  gms. 

Selenium  Ruby,  Light  and  Rose  Colored 

Arsenic     200.0  gms. 

Sand     100.0  kgm. 

Potash,   80-85  percent    ::4 . 0  kgm. 

CaCGv    17.0  kgm. 

Selenium    nitrate     120.0  gms. 

"  [bid    12,    p.    126. 


8  DEVELOPMENT  OF  RUBY  COLOR  IN  GLASS 

In  the  reds  with  sulphur,  one  should  not  use  the  alkali  sul- 
phates, hut  only  sulphur  with  charcoal  as  a  reducing  agent.  The 
charcoal  keeps  the  sulphur  from  combining  with  the  soda  and 
potash.  In  sulphur  ruby,  a  great  part  of  the  sulphur  vaporizes 
in  the  working.  The  melting  glass  foams  vigorously,  and  there- 
fore one  should  fill  the  pot  only  half  full  at  first,  and  after  the 
batch  reaches  quiet  fusion,  put  in  the  second  half. 

Sulphur  ruby  is  hard  to  make  in  uniform  colors,  and  dark- 
ens in  the  muffle.  It  is  not  used  for  making  higher  grades  of 
glass.     Two  batches  for  sulphur  ruby  are  given  : 

Xo.  1  No.  2 

Sand    100.0  kgm.  100.0  kgm. 

Soda    45.0  kgm.  45.0  kgm. 

CaCO.3     20.0  kgm.  20.0  kgm. 

Flowers    of    sulphur    7.0  kgm.  10.0  kgm. 

Antimony    sulphate     5.0  kgm. 

Charcoal    2.0  kgm. 

EXPERIMENTAL    DATA    BY    WRITER 

The  foregoing  typical  batches  for  ruby  glass  are  but  a  few 
of  a  large  number  given  in  the  literature  pertaining  to  glass 
making.  An  examination  of  these  shows  a  wide  variation  in  com- 
position, but  all  agree  in  that  they  are  high  in  silica  and  contain 
tin.  In  copper  ruby,  the  amounts  of  copper  and  tin  vary  widely 
in  their  ratios  to  each  other.  These  copper  rubies  are  probably 
used  in  the  manufacture  of  flashed  glass. 

In  the  beginning  of  the  following  experimental  work,  sam- 
ples of  commercial  copper  ruby,  both  the  quick-cooled  colorless 
and  ruby  colored  were  obtained.  The  uncolored  sample  was 
broken  into  fragments,  and  different  fragments  were  heated  to 
different  temperatures  for  various  lengths  of  time.  A  small 
lloskins  electric  furnace  was  used,  and  temperatures  were  read 
with  a  Leeds  Northrup  potentiometer,  using  a  platinum,  plati- 
num-rhodium thermocouple. 


DEVELOPMENT  OF  RUBY  COLOR  IN  GLASS 

The  following  results  were  obtained: 

TABLES 


PIECE 

MAXIMUM 
TEMPERA- 

TIME    HELD 
AT      MAX. 

REMARKS 

TURE 

TEMP. 

°0 

minutes 

1 

500 

30 

No   change   in   color 

2 

500 

60 

No   change   in   color 

3 

550 

30 

No   change   in   color 

4 

550 

60 

No   change   in   color 

5 

575 

1 

No   change   in   color 

6 

575 

30 

No   change   in   color 

7 

600 

1 

Very  light  amber 

8 

600 

15 

\  cry   light   amber 

9 

600 

30 

Bright  amber,  slightly  darker 
than   No.  8 

10 

600 

60 

Bright  amber,    same   as   No.   9 

11 

650 

1 

Bright   amber,   same   as   No.   9 

12 

650 

30 

Deep  ruby,  edges  slightly  soft- 
ened 

13 

650 

60 

Same  as  No.  12,  edges  slightly 
softened 

14 

675 

15 

Same  as  No.  12,  edges  slightly 
softened 

15 

675 

30 

Same  as  No.  12,  edges  slightly 
softened 

16 

675 

60 

Darker  than  No.  15,  edges 
slightly   softened 

17 

700 

1 

Same  as  No.  10,  edges  slightly 
softened 

18 

700 

30 

Dark  red.  edges  slightly  softened 

19 

900 

30 

Grayish  purple,  opaque,  softened 
out  of  shape 

The  rate  of  increase  of  temperature  was  a  constant  factor 
in  all  of  the-e  tests,  a.s  follows:  ten  minutes  from  room  tempera- 
ture to  300°C;  300°C  to  500°C  at  rate  of  50°  per  minute:  500° C 
to  maximum  temperature  at  a  rate  of  25°  per  minute. 

The  results  seem  to  show  that  the  color  at  any  definite  tem- 
perature is  practically  constant,  and  that  the  color  change  at 
that  temperature  is  apparently  instantaneous.     However,  time  is 


10  DEVELOPMENT  OP  RUBY  COLOR  IN  GLASS 

required  for  the  temperature  to  even  up  through-out  the  thick- 
ness of  the  piece. 

It  will  be  noticed  that  the  glass  shows  signs  of  softening 
at  that  temperature  at  which  the  strong  color  develops.  This  is 
probably  the  softening  point  Zsigmondy14  refers  to  in  the  article 
previously  quoted.  It  is  observed  that  there  is  little  or  no  ap- 
parent change  in  color  brought  out  between  650°  and  675°,  giv- 
ing a  safe  range  for  an  annealing  oven. 

Most  of  the  glass  formulas  observed  were  high  in  lead  and 
in  silica.  Accordingly  the  following  formula  was  selected,  it 
being  the  upper  silica  limit  for  most  glasses : 

0.5  PbO      j 

0.5  Na20    }   3  Sl°: 

In  order  to  determine  a  suitable  method  of  working,  several 
small  batches  of  this  glass  were  fused.  The  method  adopted  was 
as  follows : 

The  glass  was  fused  in  Battersea  crucibles  in  a  small  pot 
furnace  using  gas  and  compressed  air.  The  temperature  range 
required  for  firing  and  to  make  the  glass  liquid  enough  for  pour- 
ing, was  between  1480°C  and  1520  C.  One-half  hour  was  taken 
for  complete  fusion  of  the  lead  glasses  and  one  hour  for  the  lead- 
less  glass&s. 

Not  much  trouble  was  experienced  in  reducing  the  copper 
oxide  and  preventing  oxidation.  Although  a  slight  reducing 
flame  was  used,  the  presence  of  cream  of  tartar  (about  \/%  per- 
cent) seemed  to  make  reduction  certain,  if  the  time  of  heating" 
was  not  too  long. 

When  fusion  was  complete  the  glass  was  poured  on  a  heavy 
cast  iron  plate  1  in.  thick,  and  then  rolled  to  a  thickness  varying 
from  2  to  5  m.m.  The  thinner  portions  usually  cooled  colorless, 
and  the  color  developed  in  the  thicker,  slower  cooled  portions, 
i.  e.  turning  red  or  opaque  brown  or  black. 


14  Ibid     4. 


DEVELOPMENT  OP  RUBY  COLOR  IN  GLASS 


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12  DEVELOPMENT    OP    RUBY    COLOR    IN    GLASS 

SERIES  A 

Glass  batches  were  then  made  corresponding  to  the  for- 
mulas given  in  Series  A. 

The  following  results  were  obtained : 

Number  1  — Colored  out  very  dense  opaque  grayish-brown 
color. 

Number  2— (Decreasing  the  coloring  agent.)  This  poured 
well,  and  cooled  practically  coloiless  at  5  m.m.  thick.  Softened 
out  of  shape  at  675  C  and  colored  out,  streaked  with  reddish 
color.  At  700°C.  it  became  dark  brown,  opaque  and  still 
streaked,  very  soft. 

Number  3— (Ircreasirg  tin  to  harden.).  This  poured  well 
and  was  colorless  except  for  a  pale  greenish-yellow  color  at  5 
m.m.   thick. 

Heated  to  480°C,  gives  amber  color. 
Heated  to  525° C,  gives  deep  red  color. 
Heated  to  700° C,  softened  out  of  shape  giving  a  dense, 
brown  opaque  glass.     Color  change  very  rapid. 

Number  -1— (Decreasing  the  Cu20  to  reduce  intensity  of 
color).  Color  developed  darker  than  No.  3  in  pouring,  having  a 
greenish  cast.  Heated  to  600°  C,  its  color  was  deep  opaque,  and 
nearly  black,  amber  at  550°C,  and  brown  at  575°C. 

Number  5  — Developed  a  rather  intense  brown  color  while 
pouring.  Thin  colorless  sections  gave  a  deep  greenish  brown  at 
550°C.  and  a  dense  opaque  black  at  600°C. 

Number  6— (Still  reducing  amount  of  coloring  matter). 
This  glass  poured  clear  and  colorless.  On  reheating  it  changed 
to  opaque  black  from  550°C.  to  600°C.    Color  change  very  rapid. 

Number  7— (Coloring  matter  left  out  to  test  purity  of  ma- 
terials for  iron).  This  glass  on  reheating  at  various  tempera- 
tures gave  no  change  in  color. 

The  conclusions  from  this  series  of  glasses,  (excluding  No. 
I)15  are: 

(1)     Dow  amounts  of  copper  seemed  to  increase  the  density 


'■'This  glass  w;ts   not    melted  well   enough   to   judge  results. 


DEVELOPMENT  OF  BUB'S  COLOR  IX  GLASS  L3 

or  opacity  of  the  color,  and  decrease  the  signs  of  red,  giving 
greenish  browns. 

2  An  increase  in  the  tin  in  No.  3  st  pped  the  streakiness 

>ho\vn  in  No.  2. 

3  Glass  No.  3  was  the  best  glass  in  scries  A.  giving  a 
color  ess  glass  when  poured  and  cooled  quickly.  Reheating 
showed  shades  of  good  vril  at  various  temperatures.  However, 
the  color  change  is  so  rapid,  it  would  be  difficult  to  control  uni- 
formity of  color. 

SERIES  Al 

Series  A,  was  constructed  in  order  to  obtain  harder  glasses 
than  those  in  series  A.  by  replacing  PbO  with  CaO  so  as  to  raise 
i licit-  temperatures  of  softening-,  and  to  determine  how  this  af- 
fects the  range  of  color  change. 

Glass  Xo.  1  of  this  seiies  show  imI  a  dark  brandy  color  on 
pouring,  coloring  out  quicker  than  Xo.  3  series  A,  which  con- 
tained the  same  equivalents  of  Cu  and  Sn.  This  glass  did  not 
soften  out  of  shape  on  reheating  at  700° C,  as  did  glass  No.  3, 
series  A.  but  gave  a  dense  opaque  color.  If  it  could  be  handled, 
without  coloring-  in  pressing,  this  glass  gives  a  good  transparent 
red  at  5  m.m.  thick,  upon  reheating  to  the  proper  temperature. 

•  ilas^es  Xos.  2  and  3  (reducing  Cu20).  Colored  out  quite 
dense,  on  pouring  becoming  nearly  opaque.  When  reheated 
above  600°C.  the  glass  turned  a  deep  opaque  purple. 

Glass  Xo.  -4  (reducing  Sn02).  This  glass  seemed  to  color 
out  as  rapidly  as  Xos.  2  and  3. 

The  conclusion  which  may  be  drawn  from  this  series  is  that 
the  rapidity  of  precipitation,  or  growth  of  color  is  increased,  in- 
stead of  decreased,  as  would  be  expected  by  hardening  the  glass. 

SERIES   B 

The  basal  formula  for  Ibis  scries  i^  one  of  the  published 
formulas  given  in  Sprechsaal.16  It  is  a  high  lead  low  silica 
glass,  containing  some  boras  and  is  a  much  softer  glass  than 
series  A  and  Al. 


14 


DEVELOPMENT  OF  RUBY  COLOR  IN  GLASS 


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DEVELOPMENT  OF  RUB'S  COLOR  CN  GLASS  15 

The  results  showed  this  very  markedly.  The  fusions,  made 
at  the  same  temperature  range  1480  C  and  1520  C,  were  more 
fluid  and  poured  easier. 

Numbers  1.  2.  •'$  and  4  developed  deep  opaque  glasses  when 
poured  4  to  5  m.m.  thick.  The  thinner  portions,  however,  in- 
creased in  degree  of  transparency  to  about  2  ni.ni.  at  which 
thickness  the  glasses  cooled  colorless,  hut  of  course  vrvy  brittle. 
Upon  reheating,  the  colorless  pieces  of  these  four  glasses  colored 
to  about  the  same  color  density  when  heated  to  the  same  tem- 
perature. At  500  0,  they  showed  an  amber  color  changing  to  a 
light  red  at  525°C,  and  to  a  ruby  color  at  550  C,  becoming 
opaque  at  600  ('.  Leaving  out  the  iron,  or  manganese  or  both, 
(especially  the  latter),  seemed  to  improve  the  quality  of  the  red 
and  to  give  a  less  dense  color.  This  type  of  glass  gives  a 
much  better  red  color  than  any  of  series  A,  but  it  is  impossible 
to  work  with  sections  as  thick  as  commercial  glass  pieces  would 
be  made  and  still  obtain  a  transparent  color.  However,  it  would 
work  as  a  ruby  glass  in  making  Hashed  articles  and  give  a  good 
color.  Manganese  dioxide  and  Pe203  are  detrimental  rather 
than  helpful  in  obtaining  good  colors. 

In  series  B,  Numbers  5,  (5  and  7  (in  which  SnCX  is  absent), 
the  glasses  were  more  opaque  in  all  cases.  Number  7  colors  out 
even  in  the  thin  sections  to  a  dense  black. 

In  glasses  Xos.  8,  9.  10,  11  and  12,  the  tin  was  kept  constant 
ami  the  copper  varied.  In  all  cases  the  tendency  was  to  increase 
opacity  and  the  rapidity  in  which  the  color  appeared  on  pouring. 

In  glasses  Xos.  18.  Id  and  15,  in  which  the  tin  was  increased, 
no  beneficial  results  were  obtained,  since  these  glasses  were  more 
opaque  than  the  preceding  ones  in  the  group. 

The  ruby  color  in  glasses  as  soft,  and  as  low  in  Si02  as  the 
members  of  this  group  cannot  be  controlled.  However,  when 
Bl  and  B2  were  melted,  quenched  in  water  and  remelted,  there 
was  an  improvement,  since  all  signs  of  streakiness  disappeared, 
and  the  color  became  verv  uniform  on  reheating. 


16 


DEVELOPMENT  OP  RUBY  COLOR  IN  GLASS 


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DEVELOPMENT    OF    Rl'BY    COLOB     IN    CLASS  17 

The  basis  of  this  series  obtained  from  Hohlbaum1'  is  en- 
tirely different  than  series  B.  li  is  a  lime-potash,  high  silica, 
Leadless  glass,  with  high  tin,  therefore,  a  comparatively  refrac- 
tory and  viscous  glass  at  low  temperatures.  One  hour  was  taken 
for  fusion. 

Hohlbaum's  hatch  calls  for  SnO  as  the  reducing  agent, 
cream  of  tartar  being  added  ,-is  a  precaution  to  insure  sufficienl 
reduction.  Number  C-l  was  first  made  by  substitution  of 
SnO.  for  SnO,  and  leaving  out  the  cream  of  tartar.  An  oxidized 
clear  colorless  glass  was  the  result,  giving  no  color  change  when 
reheated  beyond  the  softening  point. 

Number  C-I  was  again  made  using  SnO.  and  0.5  percent 
cream  of  tartar.  This  glass  was  exceedingly  viscous  and  quickly 
cooled  below  the  point  of  easy  pouring.  Upon  pouring  and  roll- 
ing, (although  taking  a  little  more  time),  no  color  change  took 
place,  the  glass  remaining  clear  and  colorless. 

I 'pon  reheating,  no  color  change  took  place  until 

800° C.  was   reached,    when   a    light    amber   color   was 

obtained, 
850  ( !.  gave  a  pale  reddish  brown, 
900° C.  gave  a  light  brown, 
1000  C.  softened  with  an  opaque  brown  color. 
The  red  color  was  not  good  in  this  glass  and  it  seemed  to  be 
entirely  too  refractory. 

Series  C,  Xo.  2.  (Reducing  Si02  to  soften).  This  showed 
an  improvement  in  the  working  qualities  with  no  tendency  to 
color  out  on  pouring. 

Reheating  this  glass  gave  the  following  results: 
800°C.  a  distinct  light  red, 
850°C.  a  good  ruby  color, 

!»oi)  C.  a  deep  dark   red   Dearly  opaque  when  4   m.m. 
thick. 
Series  C,  Xo.  3  (reducing  Si02  still  further)  gave  a  fusion 
which  poured  colorless  and  flowed   freely.     Reheated  to  850°  it 
showed  a   reddish  brown,  slightly  streaked.     900°  showed  a  dis- 
tinct deep  brown. 

17  Ibid    11,    p.    12">. 


18 


DEVELOPMENT    OF    RUBY    COLOR    IN    GLASS 


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DEVELOPMENT  OF  RUBY  COLOR  EN  GLASS  19 

Series  C,  No.  4  (less  Si02  than  C3).  Poured  clear  and  col- 
orless  but  when  reheated  to  850  became  more  streaked  and 
.showed  a  more  decided  brown. 

Series  C,  No.  5,  poured  clear  and  colorless  as  the  others,  bu1 
.showed  brown  streaks.  When  reheated  to  800  it  showed  a  very 
streaked  brown  color.  When  the  glass  was  remelted  and  re- 
poured  it  gave  a  very  clear  glass. 

I '[ton  reheating  this  to  Toil  ('.  the  color  came  out  a  clouded 
black,  increasing  in  intensity  with  the  reheating  temperature. 

The  foregoing  five  glasses  in  group  C  show  that: 

(1)  Reducing  the  Si02  from  4.o7  to  4.0  molecules  improved 
the  color  in  this  series.  Further  reduction,  however,  changed 
the  color  to  browns  and  then  blacks,  giving  about  the  same  range 
of  brown  and  blacks  with  3  Si02  as  series  A  gave,  having  3  SiO., 
and  small  amounts  of  copper. 

2  i  High  silica  seems  necessary  in  order  to  develop  a  good 
red  color.  The  color  change  takes  place  at  rather  high  tempera- 
tures for  a  reheating  furnace,  and  the  glass  appears  to  be  too 
viscous  for  good  working  properties.  Glasses  06,  C7  and  C8 
were  made  by  introducing  PbO  in  place  of  part  of  the  CaO  with 
the  idea  of  softening  and.  if  possible,  still  retaining  the  property 
of  not  coloring  out  on  pouring. 

C6  and  C7  in  which  0.2  PbO  replaced  0.2  CaO  showed  a  dis- 
tinct improvement  in  the  working  qualities  and  uniformity  of 
color,  although  these  glasses  colored  out  in  the  thicker  portions 
during  the  pouring;  C6  to  a  light  red  and  07  to  a  deep  ruby. 
These  glasses,  however,  were  transparent  to  a  thickness  of  8  ni.m. 
in  comparison  with  series  B,  which  were  not  transparent  in 
pieces  over  2]1.  m.m.  in  thickness. 

Reheating  clear  portions  of  CO  gave  a  good,  deep,  ruby  color 
at  650°C,  a  considerable  lowering  of  the  temperature  over  the 
leadless  glasses  for  developing  color.  This  g!ass  also  has  a  fairly 
constant  color  over  a  temperature  range  of  25°C  (625°  0.  to 
650°C). 

Series  C,  No.  7  colored  out  at  570°  to  the  same  shade  as  C6. 

8eriesC,No.  8  (Reducing  PbO  to  o.l  with  4.00SiO2).  This 
glass  gave   evidences   of   being   harder   than    the   previous   Li'lass 


20  DEVELOPMENT  OF  RUBY  COLOR  IN  GLASS 

(C7)  as  the  fusion  colored  out  a  very  little  clearer  at  6  ni.ni. 
thick  (similar  to  C6),  and  the  color. ess  portions  gave  a  deep 
clear  ruby  on  reheating  to  570:,  the  same  as  C7  and  about  603 
lower  than  C6.  This  glass  gave  the  clearest  and  best  red  ob- 
tained in  the  foregoing  work. 

Series  C.  No.  9  (in  which  0.1  PbO  was  replaced  in  C8  by 
0.1  Xa.,0  as  borax)  gave  a  glass  considerably  more  fusible,  and 
flowed  well  in  pouring.  A  very  streaked,  nearly  black,  color  de- 
veloped in  portions  over  3  m.m.  in  thickness  on  pouring.  Thin 
transparent  pieces  heated  to  75<>  gave  a  red  color,  streaked  with 
opaque  black  lines.  This  fusion,  therefore,  did  not  give  good 
results.  The  possibility  of  spoiling  the  color  by  over-heating  is 
ever  present.  It  is  possible  that  less  B203  would  give  better  re- 
sults, though  this  was  not  tried. 

Series  C,  No.  10  (0.1Na2O  replacing  0.1  CaO).  The  result- 
ing glass  was  clear  and  colorless,  showing  a  very  few  light  red 
streaks.  The  working  properties  of  the  glass  were  very  good, 
especially  in  pouring  and  cooling. 

On  heating  to  700°C  the  glass  turned  a  clear  light  red. 
625° C.  showed  a  clear  light  red. 
725° C.  showed  a  clear  light  red. 

The  color  range  of  this  glass  is  therefore  good. 

Scries  C,  No.  11  (O.lPbO  replacing  0.1  CaO  and  with  4.57 
Si02).  Results  from  this  glass  were  a  failure  as  the  fusion  was 
incomplete  and  very  viscous  and  colored  out  a  dense  opaque 
black  on  pouring.  If  properly  fused,  better  results  would  no 
doubt  have  been  obtained. 

Series  C,  No.  12  (0.1  Xa,0  replacing  0.1  CaO  and  with  1.57 
SiO„).  This  glass  gave  a  very  good  fusion,  but  was  rather  vis- 
eons  and  showed  no  color  on  pouring.  Heating  this  glass  to 
700° C  gave  an  amber  colored  glass  streaked  with  dark  red  lines. 
At  800  CC  it  showed  a  good  even  ruby  color. 

The  conclusions  from  this  last  series  of  glasses  (C6  to  C12) 
are  (1),  that  soda  replacing  lime  softened  the  glass  without 
causing  the  color  to  come  out  in  cooling.  (2)  Lead  on  the  other 
hand  caused  these  glasses  to  color  out  rapidly  on  cooling,  but 
did  not  make  them  opaque. 


DEVELOPMENT  OK  RUBY  COLOR  IN  GLASS  21 

General  Conclusions.  The  following  are  general  conclu- 
sions one  may  draw  from  this  work  regarding  the  composition 
of  a  workable  ruby  glass.  A  workable  ruby  glass  is  one  which 
will  not  color  out  when  eooled  at  the  rale  obtained  in  the  press- 
ing process,  and  yet  will  give  a  workable  range  of  temperature 
for  reheating  to  a  uniform  color  at  temperatures  below  700°. 

1st.  Highly  fluid  glasses  will  color  out  rapidly,  viscous 
glasses  slowly. 

2nd.  Replacing  lime  with  either  lead  or  soda,  increases  the 
rapidity  of  color  development,  lead  more  so  than  soda. 

3d.  High  SiOo  is  necessary  for  good  color,  low  Si02  gives  a 
tendency  towards  brown  or  black,  and  opacity. 

4th.  High  SiOo  (4.0  to  4.5  mol.),  is  necessary  to  give  suffi- 
cient viscosity. 

5th.  With  high  silica,  lime-potash  glasses  the  tendency  to 
streakiness  increases.  Small  amounts  of  lead  reduce  streaki- 
ness. 

6th.  The  glass  giving  the  best  color  in  series  B  is  No.  4. 
Glasses  Xos.  1,  2,  10  and  12  of  Series  C,  most  nearly  approached 
the  requirements  of  a  good  ruby  glass.  They  could  all  be  poured 
without  the  color  developing,  and  on  reheating,  the  color  devel- 
oped at  favorable  temperatures.  Glasses  Nos.  6  and  8,  Series  C 
gave  the  most  transparent  colors. 

7th.  Iron  and  manganese  are  detrimental  to  a  good  red 
color. 

8th.  Remelting  improves  the  uniformity  of  the  color  which 
indicates  that  streakiness  is  due  to  lack  of  homogeneity. 

9th.  Density  of  color  is  apparently  increased  with  an  in- 
crease in  temperature.  Time  is  evidently  not  an  important  fac- 
tor in  this  case. 

DISCUSSION 

Prof.  Silverman:  There  are  a  number  of  points  in  Mr. 
Williams'  paper  about  which  T  wish  to  inquire.  In  the  first 
place,  he  speaks  of  the  coloring  out  in  the  high-silica  copper  rub- 
ies. I  should  like  to  ask  whether  Mr.  Williams  found  any  direct 
bearing  by  the  alkali  content  of  the  glass.     There  is  a  claim 


22  DEVELOPS  ENT  OE  RUBY  COLOR  IN  GLASS 

made  at  present  that  a  copper  ruby  can  be  manufactured,  which 
is  a  ruby,  out  of  the  pot.  I  believe  his  views  correspond  with 
mine  in  that  the  red  color  produced  is  due  to  high  alkali  in  the 
glass.  In  other  words,  the  glass  colors  out  while  cooling  in  the 
mold,  or  even  earlier.,  Then  as  to  tin  as  a  reducing  agent,  I  can 
corroborate  these  statements  also,  having  had  the  experience 
that  tin  alone  in  connection  with  copper  gives  a  rich  color,  while 
with  manganese  and  iron  the  color  is  off.  Tin  has  to  be  con- 
trolled very  carefully.  If  you  get  below  a  certain  point  you 
obtain  a  glass  which  does  not  color  sufficiently;  and  if  you  go 
above  you  get  what  is  called  clouding  or  a  livery  color. 

I  would  like  to  ask.  to  what  Mr.  Williams  attributes  lack  of 
uniformity  of. color;  and  whether  he  feels  that  a  melt  over  a 
short  duration,  like  thirty  minutes  could  give  a  homogeneous 
glass. 

Mr.  Williams:  To  answer  the  last  question  first:  the  uni- 
formity of  color  in  my  glasses  was  not  obtained  in  the  first  melt. 
There  were  signs  of  streakiness  at  first,  but  upon  remelting, 
good  clear  colors  were  obtained.  It  is  probably  the  mechanical 
handling  of  the  glass,  or  the  duration  of  the  melt  which  has  a 
tendency  to  make  the  glass  cloudy  or  clear. 

The  first  question  you  asked,  regarding  the  high  alkali  con- 
tent, I  did  not  quite  understand,  however  I  will  make  this  point, 
that  when  I  used  lead,  replacing  the  alkali,  it  caused  the  colors 
to  come  out  more  quickly  in  the  handling.  The  color  was  just 
as  good,  in  fact  a,  little  better,  but  density  of  color  could  not  he 
controlled.  Lead  improved  the  uniformity  of  the  color  but  gave 
a  tendency  toward  opacity.  If  you  do  not  want  the  color  to 
come  out  during  pressing,  it  is  necessary  to  keep  away  from  lead. 

Prof.  Silverman:  I  should  like  to  know  further,  what  the 
object  is  in  trying  to  prevent  the  color  from  coming  out  during 
pressing. 

Mr.  Williarks:  If  you  do  not  prevent  it,  the  different  var- 
iations in  the  cooling  of  the  mold  would  not  give  the  same  shad- 
ing of  red  in  the  finished  pieces. 

Prof..  SilnrnKin:  But  do  you  not  get,  the  same  effect  by 
heating  to  a  certain  temperature  afterwards? 


DEVELOPMENT    OF    UIT.V    COLOR    IN    GLASS  23 

Mr.  Williams:  Fee;  bu1  can  you  control  the  rate  of  cooling 
of  glass  in  the  mold  sufficiently  accurately  as  to  give  uniformity 
of  color  from  piece  to  piece .' 

Prof.  Silverman:  1  cannol  quite  see  bow  that  lias  a  bearing 
mi  the  rate  of  cooling.  Suppose  your  glass  does  ool  color  out 
below  700°.  You  mighl  have  a  mold  anywhere  from  400  to 
600  ,  and  the  fact  that  you  have  no  color  would  be  oo  indication 
thai  your  mold  temperature  is  correct.  In  other  words,  you 
have  .such  a  largo  range  below  the  coloring-out  temperature  that 
it  dues  not  seem  any  better  indication  as  to  mold  temperature, 
than  if  you  had  a  glass  that  colored  out,  except  possibly  to  tell 
you  that  the  mold  is  too  hot. 

Mr.  WiUiams:  My  experience  with  glass  that  colored  ou1 
was  that  glass  of  various  thicknesses  was  different  in  shade.  Tin? 
difference  in  temperature  of  a  mold  would  influence  the  color. 
'The  coloring  out  at  a  definite  temperature  also  depends  upon 
the  speed  at  which  a  glass  cools  through  the  small  temperature 
range  of  color  development.  If  the  glass  cools  at  a  high  rate  of 
speed  through  this  temperature,  the  colloidal  copper  would  not 
come  out  in  large  enough  particles  to  show  color.  If  the  cooling 
rate  is  slower  the  particles  grow  of  sufficient  size  to  give  color. 

Mr.  Gelstharp:  I  should  like  to  ask  whether  that  was  not 
sub-oxide  of  copper. 

Mr.   WilUams:     I  used  cuprous  oxide. 

Prof.  SI  nil:  Perhaps  I  might  throw  a  little  light  on  Prof. 
Silverman's  question  by  stating,  that  among  the  things  .Mi-.  Wil- 
liams is  investigating  is  a  study  of  the  temperatures  at  which 
the  copper  ruby  comes  out,  and  the  effect  of  length  of  time  as 
well  ;is  temperature  in  bringing  it  out.  That  is  why  he  is  trying 
to  secure  colorless  glass  to  begin  with. 


